Organic electroluminescent element, display device and lighting device

ABSTRACT

Provided is an organic electroluminescent element comprising a substrate having thereon an anode, a cathode, and a plurality of organic layers sandwiched between the anode and the cathode,
         wherein the plurality of organic layers comprise:   a light emitting layer containing a phosphorescence emitting compound; and   an electron transport layer containing a compound represented by Formula (1),       

       (Ar1) n 1−Y1  Formula (1)
         wherein n1 is an integer of 1 or more; Y 1  is a substituent when n1 is 1, and Y 1  is a single bond or a linking group of n1 valences when n1 is two or more; Ar1 is a group represented by Formula (A), a plurality of Ar1 may be the same or different with each other when n1 is two or more; and the compound represented by Formula (1) contains at least two condensed aromatic heterocyclic rings each comprising 3 or more rings condensed with each other:

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/463,250 filed on May 8, 2009, which claims priority toJapanese Patent Application No. 2008-125814 filed on May 13, 2008, No.2008-295408 filed on Nov. 19, 2008, No. 2009-11533 filed May 12, 2009,and No. 2009-073509 filed on Mar. 25, 2009 with the Japan Patent Office,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent element,a display device and a lighting device.

BACKGROUND

Conventionally, an emission type electronic display device includes anelectroluminescence display (hereinafter, referred to as an ELD). Aconstituent element of an ELD includes such as an inorganicelectroluminescent element and an organic electroluminescent element(hereinafter, referred to as an organic EL element).

An inorganic electroluminescent element has been utilized as a flatlight source, however, it requires a high voltage of alternating currentto operate an emission element. An organic electroluminescent element isan element provided with a constitution comprising a light emittinglayer containing a emitting substance being sandwiched with a cathodeand an anode, and an exciton is generated by an electron and a positivehole being injected into the light emitting layer to be recombined,resulting emission utilizing light release(fluorescence.phosphorescence) at the time of deactivation of saidexciton; the emission is possible at a voltage of approximately a few toa few tens volts, and an organic electroluminescent element isattracting attention with respect to such as superior viewing angle andhigh visual recognition due to a self-emission type as well as spacesaving and portability due to a completely solid element of a thin layertype.

However, in an organic electroluminescence in view of the futurepractical application, desired has been development of an organic μLelement which efficiently emits at a high luminance with a low electricconsumption.

In Japanese Patent No. 3093796, a slight amount of a fluorescentsubstance has been doped in a stilbene derivative, distyrylarylenederivative or a tristyrylarylene derivative, to achieve improvedemission luminance and a prolonged lifetime of an element.

Further, there are known such as an element having an organic lightemitting layer comprising a 8-hydroxyquinoline aluminum complex as ahost compound which is doped with a slight amount of a fluorescentsubstance (for example, JP-A 63-264692) and an element having an organiclight emitting layer comprising a 8-hydroxyquinoline aluminum complex asa host compound which is doped with quinacridone type dye (for example,JP-A 3-255190).

In the case of utilizing emission from an excited singlet as describedabove, since a generation ratio of a singlet exciton to a tripletexciton is ⅓, that is, a generation probability of an emitting excitonspecies is 25% and a light taking out efficiency is approximately 20%,the limit of an external quantum efficiency (next) of taking out lightis said to be 5%.

However, since an organic EL element which utilizes phosphorescence froman excited triplet has been reported from Princeton University (M. A.Baldo et al., Nature vol. 395, pp. 151-154 (1998)), researches onmaterials exhibiting phosphorescence at room temperature have come to beactive.

For example, it is also disclosed in A. Baldo et al., Nature, vol. 403,No. 17, pp. 750-753 (2000), and U.S. Pat. No. 6,097,147.

Since the upper limit of internal quantum efficiency becomes 100% byutilization of an excited triplet, which is principally 4 times of thecase of an excited singlet, it may be possible to achieve almost thesame ability as a cooled cathode ray tube to attract attention also foran illumination application.

For example, in such as S. Lamansky et al., J. Am. Chem. Soc., vol. 123,p. 4304 (2001), many compounds mainly belonging to heavy metal complexessuch as iridium complexes have been synthesized and studied.

Further, in the aforesaid, A. Baldo et al., Nature, vol. 403, No. 17,pp. 750-753 (2000), utilization of tris(2-phenylpyridine)iridium as adopant has been studied.

An orthometalated complex provided with platinum instead of iridium as acenter metal is also attracting attention. With respect to these typesof complexes, many examples having a characteristic ligand are known.

Carbazole derivatives such as CBP and m-CP are well know as a hostcompound for these phosphorescence emitting compounds, (for example,refer to WO 03/80760 and WO 04/74399).

Especially, m-CP or its derivatives having a large band gap are knownfor a host compound used for blue light emission.

There is disclosed a technology which enables to produce a highluminance light by introduction of a positive hole inhibiting layer (anexciton inhibiting layer). An example of which is disclosed by PioneerCo. Ltd. In this example, a specific aluminium complex or a fluorinatedcompound is used to produce an emission with high efficiency (forexample, refer to Patent Document 1).

Another example was disclosed in which a pyridine derivative or apyrimidine derivative was used in an electron transport layer (forexample, refer to Patent Documents 2 and 3). Further examples which usea pyridine derivative in an electron transport layer are known (forexample, refer to Patent Documents 4 and 5).

However, disclosed technologies are still insufficient for realizing apractical organic electroluminescent element, and further improvement isrequested.

-   Patent Document 1: Unexamined Japanese patent application    publication (hereafter it is called as JP-A) 2002-8860.-   Patent Document 2: WO 06/103909-   Patent Document 3: JP-A 2003-45662-   Patent Document 4: JP-A 04-68076-   Patent Document 5: U.S. Pat. No. 5,077,142

SUMMARY

An object of the present invention is to provide an organicelectroluminescent element which can be driven with a low drivingvoltage and exhibits high emission luminance. Further object of thepresent invention is to provide a lighting device and a display deviceusing the same organic electroluminescent element.

An object of the present invention described above has been achieved bythe following constitutions.

1. An organic electroluminescent element comprising a substrate havingthereon an anode, a cathode, and a plurality of organic layerssandwiched between the anode and the cathode,

wherein the plurality of organic layers comprise:

a light emitting layer containing a phosphorescence emitting compound;and

an electron transport layer containing a compound represented by Formula(1),

(Ar1)n1−Y1  Formula (1)

wherein n1 is an integer of 1 or more; Y1 is a substituent when n1 is 1,and Y1 is a single bond or a linking group of n1 valences when n1 is twoor more; Ar1 is a group represented by Formula (A), a plurality of Ar1may be the same or different with each other when n1 is two or more; andthe compound represented by Formula (1) contains at least two condensedaromatic heterocyclic rings each comprising 3 or more rings condensedwith each other:

wherein X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 each are —C(R1)═or —N═; R, R′ and R1 each are a hydrogen atom, a substituent or abonding site to Y1, (*) is a bonding site to Y1; Y2 is a single bond ora bivalent linking group; Y3 and Y4 each are a group derived from a 5 or6 membered aromatic ring, at least one of Y3 and Y4 is derived from anaromatic heterocyclic ring containing a nitrogen atom in the ring; andn2 is an integer of 1 to 4.

2. The organic electroluminescent element of the aforesaid item 1,

wherein n1 of Formula (1) is an integer of 2 or more.

3. The organic electroluminescent element of the aforesaid items 1 or 2,wherein Y2 of Formula (A) is a single bond.

4. The organic electroluminescent element of any one of the aforesaiditems 1 to 3,

wherein n2 in Formula (A) is an integer of 1 or 2.

5. The organic electroluminescent element of any one of the aforesaiditems 1 to 4,

wherein,

-   -   (i) X of Formula (A) is —N(R)—, and R is a bonding site to Y1;        or    -   (ii) (ii) E3 is —C(R1)═, and R1 is a bonding site to Y1.

6. The organic electroluminescent element of any one of the aforesaiditems 1 to 5,

wherein, Y1 is a group derived from a condensed aromatic heterocyclicring comprising 3 or more rings condensed with each other.

7. The organic electroluminescent element of the aforesaid item 6,

wherein, Y1 is a group derived from a dibenzofuran ring or adibenzothiophene ring.

8. The organic electroluminescent element of any one of the aforesaiditems 1 to 7,

wherein at least 6 of E1 to E8 of Formula (A) each are —C(R1)═.

9. The organic electroluminescent element of any one of the aforesaiditems 1 to 8,

wherein Y3 of Formula (A) is a group derived from a 6 membered aromaticring.

10. The organic electroluminescent element of any one of the aforesaiditems 1 to 9,

wherein Y4 of Formula (A) is a group derived from a 6 membered aromaticring.

11. The organic electroluminescent element of any one of the aforesaiditems 1 to 10,

wherein Y4 of Formula (A) is a group derived from an aromaticheterocyclic ring containing a nitrogen atom in the ring.

12. The organic electroluminescent element of the aforesaid item 11,

wherein Y4 of Formula (A) is a group derived from a pyridine ring.

13. The organic electroluminescent element of any one of the aforesaiditems 1 to 12,

wherein Y3 of Formula (A) is a group derived from a benzene ring.

14. The organic electroluminescent element of the aforesaid item 1,

wherein the compound represented by Formula (1) is further representedby Formula (2):

wherein Y5 is a divalent linking group of an aryrene group, aheteroaryrene group or a combination group thereof; E51 to E66 each are—C(R3)═ or —N═, R3 is a hydrogen atom or a substituent; Y6 to Y9 eachare a group derived from an aromatic hydrocarbon ring or an aromaticheterocyclic ring, provided that at least one of Y6 and Y7 and at leastone of Y8 and Y9 each are a group derived form an aromatic heterocyclicring containing a nitrogen atom in the ring; and n3 and n4 each are aninteger of 0 to 4, provided that a sum of n3 and n4 is an integer of 2or more.

15. The organic electroluminescent element of the aforesaid item 14,

wherein Y5 of Formula (2) is a group derive from a condensed aromaticheterocyclic ring comprising 3 or more rings condensed with each other.

16. The organic electroluminescent element of the aforesaid item 15,

wherein Y5 of Formula (2) is a group derived from a dibenzofuran ring ora dibenzothiophene ring.

17. The organic electroluminescent element of any one of the aforesaiditems 14 to 16,

wherein at least 6 of E51 to E58 and at least 6 of E59 to E66 of Formula(2) are —C(R3)═.

18. The organic electroluminescent element of any one of the aforesaiditems 14 to 17,

wherein Y7 and Y9 of Formula (2) each are a group derived from anaromatic heterocyclic ring containing a nitrogen atom in the ring.

19. The organic electroluminescent element of the aforesaid item 18,

wherein Y7 and Y9 of Formula (2) each are a group derived from apyridine ring.

20. The organic electroluminescent element of any one of the aforesaiditems 14 to 19,

wherein Y6 and Y8 of Formula (2) each are a group derived from a benzenering.

21. The organic electroluminescent element of any one of the aforesaiditems 14 to 20,

wherein n3 and n4 of Formula (2) each are an integer of 1 to 2, providedthat a sum of n3 and n4 is an integer of 2 or more.

22. The organic electroluminescent element of the aforesaid item 14,

wherein the compound represented by Formula (2) is further representedby Formula (3):

wherein Y5 is a divalent linking group of an aryrene group, aheteroaryrene group or a combination group thereof; E51 to E66 and E71to E88 each are —C(R3)═ or —N═, R3 is a hydrogen atom or a substituent,provided that at least one of E71 to E79 and at least one of E80 to E88each are —N═; and n3 and n4 each are an integer of 0 to 4, provided thata sum of n3 and n4 is an integer of 2 or more.

23. The organic electroluminescent element of the aforesaid item 22,

wherein Y5 of Formula (3) is a group derive from a condensed aromaticheterocyclic ring comprising 3 or more rings condensed with each other.

24. The organic electroluminescent element of the aforesaid item 23,

wherein Y5 of Formula (3) is a group derived from a dibenzofuran ring ora dibenzothiophene ring.

25. The organic electroluminescent element of any one of the aforesaiditems 22 to 24,

wherein at least 6 of E51 to E58 and at least 6 of E59 to E66 of Formula(3) each are —C(R3)═.

26. The organic electroluminescent element of any one of the aforesaiditems 22 to 25,

wherein at least one of E75 to E79 and at least one of E84 to E88 ofFormula (3) each are —N═.

27. The organic electroluminescent element of the aforesaid item 26,

wherein only one of E75 to E79 and only one of E84 to E88 of Formula (3)each are —N═.

28. The organic electroluminescent element of any one of the aforesaiditems 22 to 27,

wherein E71 to E74 and E80 to E83 of Formula (3) each are —C(R3)═.

29. The organic electroluminescent element of any one of the aforesaiditems 22 to 28,

wherein n3 and n4 of Formula (3) each are an integer of 1 to 2, providedthat a sum of n3 and n4 is an integer of 2 or more.

30. The organic electroluminescent element of any one of the aforesaiditems 1 to 29,

wherein the phosphorescence emitting compound contained in the lightemitting layer is a compound represented by Formula (4):

wherein P and Q each are a carbon atom or a nitrogen atom; A1 is a groupof atoms which forms an aromatic hydrocarbon ring or an aromaticheterocyclic ring together with P—C; A2 is a group of atoms which formsan aromatic heterocyclic ring together with Q-N; P1-L1-P2 is a bidentateligand, P1 and P2 each independently are a carbon atom, an nitrogen atomor an oxygen atom, L1 is a group of atoms which forms a bidentate ligandtogether with P1 and P2; j1 is an integer of 1 to 3; j2 is an integer of0 to 2, provided that a sum of j1 and j2 is 2 or 3; and M1 is atransition metal of Groups 8 to 10 of the Element Periodic Table.

31. The organic electroluminescent element of the aforesaid item 30,

wherein the compound represented by Formula (4) is further representedby Formula (5):

wherein Z is a hydrocarbon ring or a heterocyclic ring; A1 is a group ofatoms which forms an aromatic hydrocarbon ring or an aromaticheterocyclic ring together with P—C; A3 is —C(R01)═C(R02)-, —N═C(R02)-,—C(R01)═N— or —N═N—, R01 and R02 each are a hydrogen atom or asubstituent; P1-L1-P2 is a bidentate ligand, P1 and P2 eachindependently are a carbon atom, an nitrogen atom or an oxygen atom, L1is a group of atoms which forms a bidentate ligand together with P1 andP2; j1 is an integer of 1 to 3; j2 is an integer of 0 to 2, providedthat a sum of j1 and j2 is 2 or 3; and M1 is a transition metal ofGroups 8 to 10 of the Element Periodic Table.

32. The organic electroluminescent element of the aforesaid items 30 or31,

wherein M1 of Formula (4) is iridium.

33. The organic electroluminescent element of any one of the aforesaiditems 1 to 32,

wherein the electron transport layer is produced by a step of formingthe layer using a wet process.

34. The organic electroluminescent element of any one of the aforesaiditems 1 to 33,

wherein the light emitting layer is produced by a step of forming thelayer using a wet process.

35. The organic electroluminescent element of any one of the aforesaiditems 1 to 34 emitting a white light.

36. A lighting device provided with the organic electroluminescentelement of any one of the aforesaid items 1 to 35.

37. A display device provided with the organic electroluminescentelement of any one of the aforesaid items 1 to 36.

The present invention has enabled to provide an organicelectroluminescent element which can be driven with a low drivingvoltage and exhibits high emission luminance. The present invention hasalso enabled to provide a lighting device and a display device using thesame organic electroluminescent element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing to show an example of a display deviceconstituted of an organic EL element.

FIG. 2 is a schematic drawing of a display section A.

FIG. 3 is a schematic drawing of a pixel.

FIG. 4 is a schematic drawing of a full-color display device driven witha passive matrix method.

FIG. 5 is a schematic drawing of a lighting device.

FIG. 6 is a schematic cross-sectional view of a lighting device.

FIG. 7 is a schematic constitutional view of an organic EL full-colordisplay device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the organic electroluminescent element of the present invention, byachieving the constitution specified via any one of Items 1-37, it waspossible to prepare an organic electroluminescent element which resultedin high light emission efficiency, a long light emitting lifetime, andlow drive voltage (also referred to as a low voltage increase ratio).

Further, by employing the organic EL element exhibiting the aforesaidcharacteristics, it was possible to produce a display device of highluminance, and a lighting device.

Each of the components according to the present invention will now besequentially detailed.

The inventors of the present invention conducted diligent investigationof the molecular structure of heterocyclic derivatives, such as apyridine derivative or a pyrimidine derivative, which have, heretofore,been known as an electron transport material. As a result, it wasdiscovered that by employing at least one of the compounds representedby aforesaid Formula (1), it was possible to provide an organicelectroluminescent element (hereinafter also referred to as an organicEL element) which resulted in a high light emission efficiency, a longlight emission lifetime, and low drive voltage (also referred to as lowvoltage increasing ratio), as well as a lighting device and a displaydevice incorporating the aforesaid organic EL element.

In addition, by combining the aforesaid compounds, it was possible toproduce a highly efficient full-color image display device.

The organic EL element is an organic electroluminescent element which isstructured in such a manner that a plurality of organic compound layersis sandwiched between the anode and the cathode, and one of theplurality of organic compound layers is a light emitting layerincorporating phosphorescence emitting compounds, while another layer isan electron transport layer. The aforesaid electron transport layer ischaracterized in incorporating the compounds represented by aforesaidFormula (1).

An essential requirement to realize the effects described in the presentinvention is that the electron transport layer, which constitutes theorganic EL element of the present invention, incorporates the compoundsrepresented by aforesaid Formula (1).

Further, in view of transport balance of a carrier, it is notappropriate to employ the compounds represented by Formula (1) accordingto the present invention in a bipolar layer (for example, a lightemitting layer) which transports both positive holes and electrons as alight emitting host does, due to the high electron transportability.

The constitution layers of an organic EL element of the presentinvention, such as a light emitting layer and an electron transportlayer, will be detailed in the following section describing theconstitution layers of an organic EL element.

<Compound Represented by Formula (1)>

The compound represented by Formula (1) of the present invention will bedescribed. In Formula (1), examples of the substituents represented byY1 include: an alkyl group (for example, a methyl group, an ethyl group,a propyl group, an isopropyl group, a tert-butyl group, a pentyl group,a hexyl group, an octyl group, a dodecyl group, a tridecyl group, atetradecyl group and a pentadecyl group); a cycloalkyl group (forexample, a cyclopentyl group and a cyclohexyl group); an alkenyl group(for example, a vinyl group, an allyl group, a 1-propenyl group, a2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group and anisopropenyl group); an alkynyl group (for example, an ethynyl group anda propargyl group); an aromatic hydrocarbon ring group (also called anaromatic carbon ring or an aryl group, for example, a phenyl group, ap-chlorophenyl group, a mesityl group, a tolyl group, a xylyl group, anaphthyl group, an anthryl group, an azulenyl group, an acenaphthenylgroup, a fluorenyl group, a phenanthryl group, an indenyl group, apyrenyl group and a biphenyryl group); an aromatic heterocyclic group(for example, a furyl group, a thienyl group, a pyridyl group, apyridazinyl group, a pyrimidinyl group, a pyrazinyl group, a triazinylgroup, an imidazolyl group, pyrazolyl group, a thiazolyl group, aquinazolinyl group, a carbazolyl group and a carbolinyl group, adiazacarbazolyl group (which is a group in which one of the carbon atomsconstituting the carboline ring of the above carbolinyl group isreplaced with a nitrogen atom) and a phtharazinyl group); a heterocyclicgroup (for example, a pyrrolidyl group, an imidazolidyl group, amorpholyl group, and an oxazilidyl group); an alkoxyl group (forexample, a methoxy group, an ethoxy group, a propyloxy group, apentyloxy group, an hexyloxy group, an octyloxy group and a dodecyloxygroup); a cycloalkoxy group (for example, a cyclopentyloxy group and acyclohexyloxy group); an aryloxy group (for example, a phenoxy group anda naphthyloxy group); an alkylthio group (for example, a methylthiogroup, an ethylthio group, a propylthio group, a pentylthio group, ahexylthio group, an octylthio group and a dodecylthio group); acycloalkylthio group (for example, a cyclopentylthio group and acyclohexylthio group); an arylthio group (for example, a phenylthiogroup and a naphthylthio group); an alkoxycarbonyl group (for example, amethyloxycarbonyl group, an ethyloxycarbonyl group, a butyloxycarbonylgroup, an octyloxycarbonyl group and a dodecyloxycarbonyl group); anaryloxycarbonyl group (for example, a phenyloxycarbonyl group and anaphthyloxycarbonyl group); a sulfamoyl group (for example, anaminosulfonyl group, a methylaminosulfonyl group, adimethylaminosulfonyl group, a butylaminosulfonyl group, ahexylaminosulfonyl group, a cyclohexylaminosulfonyl group, anoctylaminosulfonyl group, a dodecylaminosulfonyl group, aphenylaminosulfonyl group, a naphthylaminosulfonyl group and a2-pyridylaminosulfonyl group); an acyl group (for example, an acetylgroup, an ethylcarbonyl group, a propylcarbonyl group, a pentylcarbonylgroup, a cyclohexylcarbonyl group, an octylcarbonyl group, a2-ethylhexylcarbonyl group, a dodecylcarbonyl group, a phenylcarbonylgroup, a naphthylcarbonyl group and a pyridylcarbonyl group); an acyloxygroup (for example, an acetyloxy group, an ethylcarbonyloxy group, abutylcarbonyloxy group, an octylcarbonyloxy group, a dodecylcarbonyloxygroup and a phenylcarbonyloxy group); an amido group (for example, amethylcarbonylamino group, an ethylcarbonylamino group, adimethylcarbonylamino group, a propylcarbonylamino group, apentylcarbonylamino group, a cyclohexylcarbonylamino group, a2-ethylhexylcarbonylamino group, an octylcarbonylamino group, adodecylcarbonylamino group, a phenylcarbonylamino group and anaphthylcarbonylamino group); a carbamoyl group (for example, anaminocarbonyl group, a methylaminocarbonyl group, adimethylaminocarbonyl group, a propylaminocarbonyl group, apentylaminocarbonyl group, a cyclohexylaminocarbonyl group, anoctylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, adodecylaminocarbonyl group, a phenylaminocarbonyl group, anaphthylaminocarbonyl group and a 2-pyridylaminocarbonyl group); aureido group (for example, a methylureido group, an ethylureido group, apentylureido group, a cyclohexylureido group, an octylureido group, adodecylureido group, a phenylureido group, a naphthylureido group and a2-oyridylaminoureido group); a sulfinyl group (for example, amethylsulfinyl group, an ethylsulfinyl group, a butylsulfinyl group, acyclohexylsulfinyl group, a 2-ethylhexylsulfinyl group, adodecylsulfinyl group, a phenylsulfinyl group, a naphthylsulfinyl groupand a 2-pyridylsulfinyl group); an alkylsulfonyl group (for example, amethylsulfonyl group, an ethylsulfonyl group, a butylsulfinyl group, acyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group and adodecylsulfonyl group); an arylsulfonyl group or a heteroarylsulfonylgroup (for example, a phenylsulfonyl group, a naphthylsulfonyl group anda 2-pyridylsulfonyl group); an amino group (for example, an amino group,an ethylamino group, a dimethylamino group, a butylamino group, acyclopentylamino group, a dodecylamino group, an anilino group, anaphthylamino group, a 2-pyridylamino group, a piperidyl group (it iscalled as a piperidinyl group) and a 2,2,6,6-tetramethyl piperidinylgroup); a halogen atom (foe example, a fluorine atom, a chlorine atomand a bromine atom); a fluorohydrocarbon group (for example, afluoromethyl group, a trifluoromethyl group, a pentafluoroethyl groupand a pentafluorophenyl group); a cyano group; a nitro group; a hydroxylgroup; a mercapto group; a silyl group (for example, a trimethylsilylgroup, a triisopropylsilyl group, a triphenylsilyl group and aphenyldiethylsilyl group); a phosphate group (for example,dihexylphosphoryl group); a phosphite group (for example,diphenylphosphinyl group); and a phosphono group.

These substituents may further be substituted with the aforesaidsubstituents. Further, a plurality of these substituents may mutually bejoined to form a ring.

In Formula (1), specific examples of a linking group represented by Y1and having n1 valences include: a divalent, a trivalent and atetravalent linking group.

In Formula (1), examples of a divalent linking group represented by Y1include: an alkylene group (for example, an ethylene group, atrimethylene group, a tetramethylene group, a propylene group, anethylethylene group, a pentamethylene group, and a hexamethylene group,a 2,2,4-trimethylhexamethylene group, a heptamethylene group, anoctamethylene group, nanomethylene group, a decamethylene group, aundecamethylene group, a dodecamethylene group, a cyclohexylene group(for example, 1,6-cyclohexanediyl group) and a cyclopenthylene group(for example, 1,5-cyclopentanediyl group); an alkenylene group (forexample, a vinylene group, a propenylene group, a butenylene group, apentenylene group, a 1-methylvinylene group, a 1-methylpropenylenegroup, a 2-methylpropenylene group, a 1-methylpentenylene group, a3-methylpentenylene group, a 1-ethylvinylene group, a 1-ethylpropenylenegroup, a 1-ethylbutenylene group and a 3-ethylbutenylene group); analkynylene group (for example, an ethynylene group, a 1-propynylenegroup, a 1-butynylene group, a 1-pentynylene group, a 1-hexnylene group,a 2-butynylene group, a 2-pentynylene group, a 1-methylethynylene group,a 3-methyl-1-propynylene group and a 3-methyl-1-butynylene group); anarylene group (for example, an o-phenylene group, a p-phenylene group, anaphthalenediyl group, an anthracenediyl group, a naphthacenediyl group,a pyrenediyl group, a naphthylnaphthalenediyl group, a biphenyldiylgroup (for example, a [1,1′-biphenyl]-4,4′-diyl group and a3,3′-biphenyldiyl group, and a 3,6-biphenyldiyl group), terphenyldiylgroup, quaterphenyldiyl group, a quinquephenyldiyl group, asexiphenyldiyl group, a septiphenyldiyl group, an octiphenyldiyl group,a nobiphenyldiyl group and a deciphenyldiyl group); a heteroarylenegroup (for example, a divalent group derived from the group consistingof a carbazole group, a carboline ring, a diazacarbazole ring (alsoreferred to as a monoazacarboline group, indicating a ring structureformed in such a manner that one of the carbon atoms constituting thecarboline ring is replaced with a nitrogen atom); a divalent groupderived from a ring of, for example, a triazole ring, a pyrrole ring, apyridine ring, a pyrazine ring, a quinoxaline ring, a thiophene ring, anoxadiazole ring, a dibenzofuran ring, a dibenzothiophene ring and anindole ring; and a chalcogen atom such as oxygen and sulfur; a divalentgroup derived from a ring having a condensed aromatic heterocycle with 3or more ring (which is preferably contains at least one of hetero atomsof N, O, and S), for example, an acridine ring, a benzoquinoline ring, acarbazole ring, a phenazine ring, a phenanthridine ring, aphenanthroline ring, a carboline ring, a cycladine ring, a quindolinering, a thebenidine ring, a quinindoline ring, a triphenodithiazinering, a triphenodioxazine ring, a phenanthrazine ring, an anthrazinering, a perimizine ring, a diazacarbazole ring (indicating a ringstructure formed in such a manner that one of the carbon atomsconstituting the carboline ring is replaced with a nitrogen atom), aphenanthroline ring, a dibenzofuran ring, a dibenzothiophene ring, anaphthofuran ring, a naphthothiophene ring, a benzodifuran ring, abenzodithiophene ring, a naphthodifuran ring, a naphthodithiophene ring,an anthrafuran ring, an anthradifuran ring, an anthrathiophene ring, ananthradithiophene ring, a thianthrene ring, a phenoxathiine ring and athiophanthrene ring (naphthothiophene ring).

Examples of a trivalent linking group represented by Y1 of Formula (1)include: an ethanetriyl group, a propanetriyl group, a butanetriylgroup, a pentanetriyl group, a hexanetriyl group, a heptanetriyl group,an octanetriyl group, a nonanetriyl group, a decantriyl group, anundecanetriyl group, a dodecanetriyl group, a cyclohexanetriyl group, acyclopentanetriyl group, a benzenetriyl group and a naphthalenetriylgroup.

A tetravalent linking group represented by Y1 of Formula (1) is a groupwhich has an additional linking group to the above-described a trivalentlinking group. Examples of a tetravalent linking group include: apropandiylidene group, 1,3-propandiyl-2-ylidene group, a butanediylidenegroup, a pentanediylidene group, a hexanediylidene group,

a heptanediylidene group, an octanediylidene group, a nonanediylidenegroup, a decanediylidene group, an undecanediylidene group, adodecanediylidene group, a cyclohexanediylidene group, acyclopentanediylidene group, a benzenetetrayl group and anaphthalenetetrayl group.

The above-described divalent, trivalent and tetravalent linking groupsmay have further a substituent as recited for Y1 of Formula (1).

A preferable compound represented by Formula (1) contains a groupindicated Y1 which is derived from a condensed aromatic heterocyclicgroup in which 3 or more rings are condensed with each other. Specificexamples of a condensed aromatic heterocyclic group in which 3 or morerings are condensed with each other include: a dibenzofuran ring and adibenzothiophene ring. Further, n1 is preferably 2 or more.

The compound represented by Formula (1) preferably contains at least twocondensed aromatic heterocyclic groups each having 3 or more ringscondensed with each other.

When Y1 represents an n1 valent linking group, Y1 is required to benon-conjugated is order to keep the excited triplet energy of thecompound represented by Formula (1) to be high. Further, from theviewpoint of improving Tg (glass transition temperature), Y1 ispreferably composed of an aromatic ring (an aromatic hydrocarbon and anaromatic heterocycle).

Here, “non-conjugated” indicates a state of bonding in which a linkinggroup is not expressed with an alternate repetition of a single bond anda double bond, or a conjugate bond between the aromatic rings whichforms a linking group is sterically disconnected.

<Group Represented by Formula (A)>

Formula (A) represents Ar1 in Formula (1).

In “—N(R)—” and “—Si(R)(R′)” represented by X of Formula (A), and“—C(R1)═” represented by E1 to E8, R, R′ and R1 each indicate the samesubstituent represented by Y1 of Formula (1).

The divalent linking group represented by Y2 of Formula (A) indicatesthe same divalent linking group represented by Y1 of Formula (1).

In Formula (A), examples of a 5 or 6 membered aromatic ring which isused to form a group for Y3 or Y4 include: a benzene ring, an oxazolering, a thiophene ring, a furan ring, a pyrrole ring, a pyridine ring, apyridazine ring, a pyrimidine ring, a pyrazine ring, the diazine ring, atriazine ring, an imidazole ring, an isoxazole ring, a pyrazole ring anda triazole ring.

More specifically, one of Y3 and Y4 is preferably a group derived from anitrogen containing aromatic heterocycle. Examples of a nitrogencontaining aromatic heterocycle include: an oxazole ring, a pyrrolering, a pyridine ring, a pyridazine ring, a pyrimidine ring, a pyrazinering, the diazine ring, a triazine ring, an imidazole ring, an isoxazolering, a pyrazole ring and a triazole ring.

(Preferred Groups Represented by Y3)

In Formula (A), the groups represented by Y3 are preferably derived fromthe above-described 6 membered aromatic rings, more preferably derivedfrom a benzene ring.

(Preferred Groups Represented by Y4)

In Formula (A), the groups represented by Y4 are preferably derived fromthe above-described 6 membered aromatic rings, more preferably derivedfrom hetero aromatic rings containing a nitrogen atom as a ring formingmember. Specifically preferable groups for Y4 are derived from apyridine ring.

(Preferred Groups Represented by Formula (A))

Preferred groups represented by Formula (A) groups are furtherrepresented by one of the following (A-1), (A-2), (A-3) and (A-4).

In Formula (A-1), X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 eachare —C(R1)═ or —N═; R, R′ and R1 each are a hydrogen atom or asubstituent. Y2 is a single bond or a bivalent linking group. E11 to E20each are —C(R2)═ or —N═, ant at least one of E11 to E20 is —N═. R2 is ahydrogen atom, a substituent or a linking site. Provided that at leastone of E11 and E12 is —C(R2)═, and R2 is a linking site. n2 is aninteger of 1 to 4. (*) is a bonding site to Y1 of Formula (1).

In Formula (A-2), X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 eachare —C(R1)═ or —N═; R, R′ and R1 each are a hydrogen atom or asubstituent. Y2 is a single bond or a bivalent linking group. E21 to E25each are —C(R2)═ or —N═. E26 to E30 each are —C(R2)═, —N═, —O—, —S— or—Si(R3)(R4)-, and at least one of E21 to E30 is —N═. R2 is a hydrogenatom, a substituent or a linking site. R3 and R4 each are a hydrogenatom or a substituent. Provided that at least one of E21 and E22 is—C(R2)═, and R2 is a linking site. n2 is an integer of 1 to 4. (*) is abonding site to Y1 of Formula (1).

In Formula (A-3), X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 eachare —C(R1)═ or —N═; R, R′ and R1 each are a hydrogen atom or asubstituent. Y2 is a single bond or a bivalent linking group. E31 to E35each are —C(R2)═, —N═, —O—, —S— or —Si(R3)(R4)-, and E36 to E40 each are—C(R2)═ or —N═. Provided that at least one of E31 to E40 is —N═. R2 is ahydrogen atom, a substituent or a linking site. R3 and R4 each are ahydrogen atom or a substituent. Provided that at least one of E32 andE33 is —C(R2)═, and R2 is a linking site. n2 is an integer of 1 to 4.(*) is a bonding site to Y1 of Formula (1).

In Formula (A-4), X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 eachare —C(R1)═ or —N═; R, R′ and R1 each are a hydrogen atom or asubstituent. Y2 is a single bond or a bivalent linking group. E41 to E50each are —C(R2)═, —N═, —O—, —S— or —Si(R3)(R4)-, and at least one of E41to E50 is —N═. R2 is a hydrogen atom, a substituent or a linking site.R3 and R4 each are a hydrogen atom or a substituent. Provided that atleast one of E42 and E43 is —C(R2)═, and R2 is a linking site. n2 is aninteger of 1 to 4. (*) is a bonding site to Y1 of Formula (1).

The groups represented by one of Formulas (A-1) to (A-4) will bedescribed subsequently.

R, R′ and R1 in —N(R)— and —Si(R)(R′)— represented by X and in —C(R1)═represented by E1 to E8 of Formulas (A-1) to (A-4) each are synonymouswith the substituents as described by Y1 of Formula (1).

In any one of Formulas (A-1) to (A-4), a divalent linking grouprepresented by Y2 is synonymous with the linking group represented by Y1of Formula (1).

R2 in —C(R2)═, represented by E11 to E20 of Formula (A-1), E21 to E30 ofFormula (A-2), E31 to E40 of Formula (A-3), and E41 to E50 of Formula(A-4), is synonymous with the substituent represented by Y1 of Formula(1).

Next, a more preferable compound represented by the aforesaid Formula(1) of the present invention will be described.

<Compound Represented by Formula (2)>

In the present invention, the compounds represented by Formula (2) arepreferable among the compounds represented by Formula (1). The compoundsrepresented by Formula (2) will be described below.

In Formula (2), an arylene group and a heteroarylene group representedby Y5 each are synonymous with an arylene group and a heteroarylenegroup described as a divalent linking group represented by Y1 in Formula(1).

A preferable divalent linking group among an arylene group, aheteroarylene group and a combined group therewith is a heteroarylenegroup. More preferable group is a group derived from a condensedaromatic heterocycle composed of 3 or more rings condensed with eachother. Specifically preferred group is a group derived from adinbenzofuran ring or a dibenzothiophene ring.

R3 in —C(R3)═ represented by E51 to E56 of Formula (2) is synonymouswith the substituent represented by Y1 of Formula (1).

In Formula (2), among groups represented by E51 to E66, it is preferablethat 6 or more groups among E51 to E58; and 6 or more groups among E59to E66 each are expressed as —C(R3)═.

In Formula (2), examples of an aromatic hydrocarbon ring which is usedto form a group for Y6 through Y9 include: a benzene ring, a biphenylring, a naphthalene ring, an azulene ring, an anthracene ring, aphenanthrene ring, a pyrene ring, a chrysene ring, a naphthacene ring, atriphenylene ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring,an acenaphthene ring, a coronene ring, a fluorene ring, a fluoanthrenering, a naphthacene ring, a pentacene ring, a perylene ring, apentaphene ring, a picene ring, a pyrene ring, a pyranthrene ring and ananthraanthrene ring.

The afore-mentioned aromatic hydrocarbon ring may have a substituentrecited for Y1 of Formula (1).

Examples of an aromatic heterocycle which is used to form a group for Y6through Y9 include: a furan ring, a thiophene ring, an oxazole ring, apyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, apyrazine ring, a triazine ring, a benzimidazole ring, an oxadiazolering, a triazole ring, an imidazole ring, a pyrazole ring, a thiazolering, an indole ring, an indazole ring, a benzimidazole ring, abenzothiazole ring, a benzoxazole ring, a quinoxaline ring, aquinazoline ring, a cinnoline ring, a quinoline ring, an isoquinolinering, a phthalazine ring naphthylidine ring, a carbazole ring, acarboline ring and a diazacarbazole ring (indicating a ring structureformed in such a manner that one of the carbon atoms constituting thecarboline ring is replaced with a nitrogen atom).

The afore-mentioned aromatic heterocycle may have a substituent recitedfor Y1 of Formula (1).

More specifically, in Formula (2), one of Y6 and Y7, one of Y8 and Y9each are preferably a group derived from a nitrogen containing aromaticheterocycle. Examples of a nitrogen containing aromatic heterocycleinclude: an oxazole ring, a pyrrole ring, a pyridine ring, a pyridazinering, a pyrimidine ring, a pyrazine ring, a triazine ring, abenzimidazole ring, an oxadiazole ring, a triazole ring, an imidazolering, a pyrazole ring, a thiazole ring, an indole ring, an indazolering, a benzimidazole ring, a benzothiazole ring, a benzoxazole ring, aquinoxaline ring, a quinazoline ring, a cinnoline ring, a quinolinering, an isoquinoline ring, a phthalazine ring naphthylidine ring, acarbazole ring, a carboline ring and a diazacarbazole ring (indicating aring structure formed in such a manner that one of the carbon atomsconstituting the carboline ring is replaced with a nitrogen atom). InFormula (2), the groups represented by Y7 and Y9 each are preferablyderived from a pyridine ring.

In Formula (2), the groups represented by Y6 and Y8 each are preferablyderived from a benzene ring.

Further, more preferable compounds represented by Formula (2) will bedescribed.

<Compound Represented by Formula (3)>

In the present invention, the compounds represented by Formula (3) arepreferable among the compounds represented by Formula (2). The compoundsrepresented by Formula (3) will be described below.

In Formula (3), an arylene group and a heteroarylene group representedby Y5 each are synonymous with an arylene group and a heteroarylenegroup deacribed as a divalent linking group represented by Y1 in Formula(1).

A preferable group among an arylene group, a heteroarylene group and acombined group therewith is a heteroaylen group. More preferable groupis a group derived from a condensed aromatic heterocycle composed of 3or more rings condensed with each other. Specifically preferred group isa group derived from a dinbenzofuran ring or a dibenzothiophene ring.

R3 in —C(R3)═ represented by E51 to E56, and E71 to E78 of Formula (3)is synonymous with the substituent represented by Y1 of Formula (1).

In Formula (3), it is preferable that 6 or more groups among E51 to E58;and 6 or more groups among E59 to E66 each are expressed as —C(R3)═.

In Formula (3), it is preferable that at least one group among E75 toE79; and at least one group among E84 to E88 each are expressed as —N═.

In Formula (3), it is preferable that only one of E75 to E79; and onlyone of E84 to E88 each are expressed as —N═.

In Formula (3), it is preferable that E71 to E74; and E80 to E83 eachare expressed as —C(R3)═.

Further, in a compound represented by

Formula (2) or Formula (3), it is preferable that E53 is expressed as—C(R3)═, and R3 is a liking site. Moreover, it is preferable that E61 isexpressed as —C(R3)═ at the same time, and in addition, and R3 is aliking site.

Further, it is preferable that E75 and E84 each are expressed as —N═;and E71 to E74, and E80 to E83 each are expressed as —C(R3)═.

Examples of a compound represented by any one of Formulas (1), (2) and(3) of the present invention will be shown, however, the presentinvention is not limited to them.

A most representative preparation method of the compound is describedbelow. However, the preparation method of the present invention is notlimited thereto.

Synthetic Example of Compound 5

Process 1: (Preparation of Intermediate compound 1)

To 300 ml of DMAc (dimethyl acetamide) were added 1.0 mol of3,6-dibromodibenzofuran, 2.0 mol of carbazole, 3.0 mol of copper powderand 1.5 mol of potassium carbonate under nitrogen atmosphere and thenwere stirred for 24 hrs at 130° C. After the reaction mixture was cooledto room temperature, 1 litter of toluene was added to the mixture andwashed the mixture 3 times with distilled water. The organic layer wasseparated and the solvent was distilled away under reduced pressure. Theobtained residue was purified with silica gel flush chromatography usingan eluent of a mixture of n-heptane and toluene (a mixing ratio of from4:1 to 3:1) resulting in obtaining Intermediate compound 1. The yieldwas 85%.

Process 2: (Preparation of Intermediate Compound 2)

To 100 ml of DMF was dissolved 0.5 mol of Intermediate compound 1 atroom temperature under atmospheric pressure, then 2.0 mol of NBS wasadded to the mixture. The mixture was stirred for one night at roomtemperature. The obtained precipitation was filtered and washed withmethanol to obtain Intermediate compound 2. The yield was 92.

Process 3: (Preparation of Compound 5)

To 3 litters of NMP (N-methyl-2-pyrrolidone) were added 0.25 mol ofIntermediate compound 2, 1.0 mol of 2-phenylpyridine, 0.05 mol ofruthenium complex [(η₆-C₆H₆)RuCl₂]₂, 0.2 mol of triphenylphosphine and12 mol of potassium carbonate under nitrogen atmosphere, and stirred forone night at 140° C.

After the reaction mixture was cooled to room temperature, 5 liters ofdichloromethane was added, then the mixture was filtered. The solvent inthe filtrate was distilled away under reduced pressure (800 Pa, 80° C.).The residue mixed with N-methyl-2-pyrrolidone was purified with silicagel flush chromatography using an eluent of a mixture of CH₂Cl₂ and Et₃N(a mixing ratio of from 20:1 to 10:1).

All of the fractions were collected and the solvent was distilled awayunder reduced pressure to obtain a residue. The obtained residue wasagain dissolved into dichloromethane and was washed 3 times with water.The organic layer was dried with magnesium sulfate and the solvent wasdistilled away under reduced pressure to produce Compound 5 in a yieldof 68%. Next, representative layer constituents of organic EL elementsof the present invention will now be detailed successively.

<Constituting Layers of Organic EL Element>

Specific examples of a preferable layer constitution of an organic ELelement of the present invention are shown below, however, the presentinvention is not limited thereto.

-   -   (i) anode/positive hole transport layer/light emitting        layer/positive hole inhibition layer/electron transport        layer/cathode    -   (ii) anode/electron inhibition layer/light emitting        layer/positive hole inhibition layer/electron transport        layer/cathode    -   (iii) anode/positive hole transport layer/electron inhibition        layer/light emitting layer/positive hole inhibition        layer/electron transport layer/cathode    -   (iv) anode/positive hole transport layer/light emitting        layer/positive hole inhibition layer/electron transport        layer/cathode buffer layer/cathode    -   (v) anode/positive hole transport layer/electron inhibition        layer/light emitting layer/positive hole inhibition        layer/electron transport layer/cathode buffer layer/cathode    -   (vi) anode/anode buffer layer/positive hole transport        layer/electron inhibition layer/light emitting layer/positive        hole inhibition layer/electron transport layer/cathode    -   (vii) anode/anode buffer layer/positive hole transport        layer/electron inhibition layer/light emitting layer/positive        hole inhibition layer/electron transport layer/cathode buffer        layer/cathode

<Electron Transport Layer>

An electron transport layer is comprised of a material having a functionto transfer an electron, and an electron injection layer and a positivehole inhibition layer are included in an electron transport layer in abroad meaning. A single layer or plural layers of an electron transportlayer may be provided.

The compound represented by any one of Formula (1), Formula (2) andFormula (3) is used in at least one of the electron transport layers ofthe present invention.

Heretofore, when an electron transport layer is composed of single layerand a plurality of layers, electron transport materials (alsofunctioning as a positive hole inhibition material) employed in theelectron transport layer adjacent to the cathode side with respect tothe light emitting layer, electrons ejected from the cathode may betransported to the light emitting layer. As such materials, any of theconventional compounds may be selected and employed. Examples of thesecompounds include such as a nitro-substituted fluorene derivative, adiphenylquinone derivative, a thiopyradineoxide derivative,carbodiimide, a fluorenylidenemethane derivative,anthraquinonedimethane, an anthraquinone derivative, an anthronederivative and an oxadiazole derivative.

Further, a thiazole derivative in which an oxygen atom in the oxadiazolering of the above-described oxadiazole derivative is substituted by asulfur atom, and a quinoxaline derivative having a quinoxaline ringwhich is known as an electron attracting group can be utilized as anelectron transport material. Polymer materials, in which these materialsare introduced in a polymer chain or these materials form the main chainof polymer, can be also utilized.

Further, a metal complex of a 8-quinolinol derivative such astris(8-quinolinol)aluminum (Alq),tris(5,7-dichloro-8-quinolinol)aluminum,tris(5,7-dibromo-8-quinolinol)aluminum,tris(2-methyl-8-quinolinol)aluminum, tris(5-methyl-8-quinolinol)aluminumand bis(8-quinolinol)zinc (Znq); and metal complexes in which a centralmetal of the aforesaid metal complexes is substituted by In, Mg, Cu, Ca,Sn, Ga or Pb, can be also utilized as an electron transport material.

Further, metal-free or metal phthalocyanine, or those the terminal ofwhich is substituted by an alkyl group and a sulfonic acid group, can bepreferably utilized as an electron transport material. Further,distyrylpyrazine derivative, which has been exemplified as a material ofan light emitting layer, can be also utilized as an electron transportmaterial, and, similarly to the case of a positive hole injection layerand a positive hole transfer layer, an inorganic semiconductor such asan n-type-Si and an n-type-SiC can be also utilized as an electrontransport material.

The electron transport layer can be prepared by forming a thin layermade of the above-described electron transport material according to amethod well known in the art such as a vacuum evaporation method, a spincoating method, a cast method, an inkjet method and a LB method. Thelayer thickness of an electron transport layer is not specificallylimited; however, it is generally 5 nm-5 □m, and preferably 5 nm-200 nm.This electron transport layer may have a single layer structurecomprised of one or not less than two types of the above describedmaterials.

Further, it is possible to employ an electron transport layer doped withimpurities, which exhibits high n property. Examples thereof includethose, described in JP-A Nos. 4-297076, 10-270172, 2000-196140,2001-102175, as well as J. Appl. Phys., 95, 5773 (2004).

The present invention is preferable since by employing an electrontransport layer of such a high n property electron transport layer, itis possible to preparer an element of further lowered electric powerconsumption.

<Light Emitting Layer>

The light emitting layer of the present invention is a layer, whichemits light via recombination of electrons and positive holes injectedfrom an electrode or a layer such as an electron transport layer or apositive hole transport layer. The emission portion may be presenteither within the light emitting layer or at the interface between thelight emitting layer and an adjacent layer thereof.

The total thickness of the light emitting layer is not particularlylimited. However, in view of the layer homogeneity, the minimization ofapplication of unnecessary high voltage during light emission, and thestability enhancement of the emitted light color against the driveelectric current, the layer thickness is regulated preferably in therange of 2 nm-5 μm, more preferably in the range of 2 nm-200 nm, butmost preferably in the range of 10-20 nm.

With regard to preparation of the light emitting layer, light emittingdopants and host compounds, described below, may be subjected to filmformation via a conventional thin filming method such as a vacuumdeposition method, a spin coating method, a casting method, an LBmethod, or an ink-jet method.

It is preferable that the light emitting layer of the organic EL elementof the present invention incorporates host compounds and at least onekind of light emitting dopants (also referred to as phosphorescencedopants or phosphorescence emitting dopants) and fluorescence dopants.

(Host Compounds (Also Referred to as Light Emitting Hosts))

Host compounds employed in the present invention will now be described.

“Host compounds”, as described in the present invention, are defined ascompounds exhibiting a phosphorescent quantum yield of thephosphorescence emission of less than 0.1 at room temperature (25° C.),more preferably less than 0.01. Further, of compounds incorporated inthe light emitting layer, it is preferable that the weight ratio in theaforesaid layer is at least 20%.

An emission host compound of the present invention may be used withplural known host compounds. It is possible to control the transfer ofcharges by making use of a plurality of host compounds, which results inhigh efficiency of an organic EL element. In addition, it is possible tomix a different emission lights by making use of a plurality of emittingdopants that will be described later. Any required emission color can beobtained thereby. It may be possible to use a conventionally known lightemitting dopant that will be described later.

Further, it may be possible to use a conventionally known light emittingdopant that will be described later. An emission host of the presentinvention may be either a low molecular weight compound or a polymercompound having a repeating unit, in addition to a low molecular weightcompound provided with a polymerizing group such as a vinyl group and anepoxy group (an evaporation polymerizing emission host).

A known emission host which may be jointly used is preferably a compoundhaving a positive hole transporting ability and an electron transportingability, as well as preventing elongation of an emission wavelength andhaving a high Tg (a glass transition temperature).

Specific examples of an emission host which may be jointly used in thepresent invention are shown below, however, the present invention is notlimited to them.

As specific examples of an emission host compounds described in thefollowing Documents are preferable. For example, JP-A Nos. 2001-257076,2002-308855, 2001-313179, 2002-319491, 2001-357977, 2002-334786,2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056,2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568,2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453,2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861,2002-280183, 2002-299060, 2002-302516, 2002-305083, 2002-305084 and2002-308837.

(Emitting Dopant)

The emitting dopant of the present invention will now be described.

As light emitting dopants according to the present invention, employedmay be fluorescent dopants (also referred to as fluorescent compounds),phosphorescence emitting dopants (also referred to as phosphorescentdopants, phosphorescent compounds, phosphorescence emitting compounds,or phosphorescent dopants). However, in view of production of organic ELelements exhibiting higher light emission efficiency, as light emittingdopants (also referred simply to as light emitting materials) employedin the light emitting layer of the organic EL element and light emittingunits in the present invention, it is preferable to simultaneouslyincorporate the aforesaid host compounds and the phosphorescenceemitting dopants.

(Phosphorescence-Emitting Dopants (Also Referred toPhosphorescence-Emitting Compounds))

A phosphorescence-emitting dopant of the present invention will bedescribed.

The phosphorescence-emitting dopant of the present invention is acompound, wherein emission from an excited triplet state thereof isobserved, specifically, emitting phosphorescence at room temperature(25° C.) and exhibiting a phosphorescence quantum yield of at least 0.01at 25° C. The phosphorescence quantum yield is preferably at least 0.1.

The phosphorescence quantum yield can be determined via a methoddescribed in page 398 of Bunko II of Dai 4 Han Jikken Kagaku Koza 7(Spectroscopy II of 4th Edition Lecture of Experimental Chemistry 7)(1992, published by Maruzen Co., Ltd.). The phosphorescence quantumyield in a solution can be determined using appropriate solvents.However, it is only necessary for the phosphorescence-emitting dopant ofthe present invention to exhibit the above phosphorescence quantum yieldusing any of the appropriate solvents.

Two kinds of principles regarding emission of a phosphorescence-emittingdopant are cited. One is an energy transfer-type, wherein carriersrecombine on a host compound on which the carriers are transferred toproduce an excited state of the host compound, and then via transfer ofthis energy to a phosphorescence-emitting dopant, emission from thephosphorescence-emitting dopant is realized. The other is a carriertrap-type, wherein a phosphorescence-emitting dopant serves as a carriertrap and then carriers recombine on the phosphorescence-emitting dopantto generate emission from the phosphorescence-emitting dopant. In eachcase, the excited state energy of the phosphorescence-emitting dopant isrequired to be lower than that of the host compound.

<Compound Represented by Formula (4)>

A phosphorescence emitting compound used in an organic EL element of thepresent invention is preferably a compound represented by theafore-mentioned Formula (4).

The compound represented by the afore-mentioned Formula (4) will bedescribed. Incidentally, a phosphorescence emitting compound (it iscalled also as a phosphorescence emitting metal complex) represented byFormula (4) is preferably contained in a light emitting layer of theorganic EL element of the present invention as a light emitting dopant.However, it may be incorporated in another constituting layer than alight emitting layer. The constituting layers other than the lightemitting layer will be detailed later.

In Formula (4), examples of an aromatic hydrocarbons which is formed byA1 with P—C include: a benzene ring, a biphenyl ring, a naphthalenering, an azulene ring, an anthracene ring, a phenanthrene ring, a pyrenering, a chrysene ring, a naphthacene ring, a triphenylene ring,o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, an acenaphthenering, a coronene ring, a fluorene ring, a fluoanthrene ring, anaphthacene ring, a pentacene ring, a perylene ring, a pentaphene ring,a picene ring, a pyrene ring, a pyranthrene ring and an anthraanthrenering.

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

In Formula (4), examples of an aromatic heterocycle which is formed byA1 with P—C include: a furan ring, a thiophene ring, an oxazole ring, apyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, apyrazine ring, a triazine ring, a benzimidazole ring, an oxadiazolering, a triazole ring, an imidazole ring, a pyrazole ring, a thiazolering, an indole ring, a benzothiazole ring, a benzoxazole ring, aquinoxaline ring, a quinazoline ring, a phthalazine ring, a carbazolering, a carboline ring and an azacarbazole ring.

An azacarbazole ring indicates a ring structure formed in such a mannerthat at least one of the carbon atoms constituting the carbazole ring isreplaced with a nitrogen atom).

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

In Formula (4), examples of an aromatic heterocycle which is formed byA2 with P—C include: an oxazole ring, an oxadiazole ring, an oxatriazolering, an isoxazole ring, a tetrazole ring, a thiadiazole ring, athiatriazole ring, an isothiazole ring, a pyrrole ring, a pyridine ring,a pyridazine ring, a pyrimidine ring, a pyrazine ring, a triazine ring,an imidazole ring, a pyrazole ring and a triazole ring.

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

In Formula (4), examples of a bidentate ligand represented by P1-L1-P2include: phenylpyridine, phenylpyrazole, phenylimidazole,phenyltriazole, phenyltetrazole, pyrazabole, acetylacetone and picolinicacid.

In Formula (4), j1 represents an integer of 1 to 3, and j2 represents aninteger of 0 to 2, provided that a sum of j1 and j2 is 2 or 3.Especially, j2 is preferable to be 0.

In Formula (4), M1 represents a transition metal element of Groups 8 to10 (it is called simply transition metal). Among them, iridium ispreferable for M1.

<Compounds Represented by Formula (5)>

The compound represented by Formula (4) of the present invention is morepreferably represented by Formula (5).

In Formula (5), examples of a hydrocarbon ring group represented by Zinclude a non-aromatic hydrocarbon ring group and an aromatichydrocarbon ring group. Examples of a non-aromatic hydrocarbon ringgroup include: a cyclopropyl group, a cyclopentyl group and a cyclohexylgroup. These groups may be unsubstituted or may be substituted with asubstituent which will be described subsequently.

Examples of an aromatic hydrocarbon ring group (it is also called as anaryl group) include: a phenyl group, p-chlorophenyl group, a mesitylgroup, a tolyl group, a xylyl group, a naphthyl group, a anthryl group,an azulenyl group, a acenaphthenyl group, a fluorenyl group, aphenanthryl group, an indenyl group, a pyrenyl group and a biphenylgroup.

The afore-mentioned groups may have a substituent represented by Y1 inFormula (1).

In Formula (5), examples of a heterocycle represented by Z include anon-aromatic heterocycle and an aromatic heterocycle. Examples of anon-aromatic heterocycle represented by Z include: an epoxy ring, anaziridine ring, a thiirane ring, an oxetane ring, an azetidine ring, athietane ring, a tetrahydrofuran ring, a dioxorane ring, a pyrrolidinering, a pyrazolidine ring, a imidazolidine ring, a oxazolidine ring, atetrahydrothiophene ring, the sulforane ring, a thiazolidine ring,□-caprolactone ring, □-caprolactam ring, a piperidine ring, ahexahydropyridazine ring, a hexahydropyrimidine ring, a piperazine ring,a morpholine ring, a tetrahydropyrane ring, a 1,3-dioxane ring, a1,4-dioxane ring, a trioxane ring, a tetrahydrothiopyrane ring, athiomorpholine ring, a thiomorpholine-1,1-dioxide ring, a pyranose ringand a diazabicyclo[2,2,2]-octane ring.

The afore-mentioned groups may have a substituent represented by Y1 inFormula (1).

Examples of an aromatic heterocycle represented by Z include: a pyridylgroup, a pyrimidinyl group, a furyl group, a pyrrolyl group, animidazolyl group, a benzimidazolyl group, a pyrrazolyl group, apyradinyl group, a triazolyl group (for example, 1,2,4-triazole-1-ylgroup, 1,2,3-triazole-1-yl group, etc.), an oxazolyl group, abenzoxazolyl group, a thiazolyl group, an isooxazolyl group, anisothiazolyl group, a furazanyl group, a thienyl group, a quinolylgroup, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, adibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinylgroup, a diazacarbazolyl group (indicating a ring structure formed insuch a manner that one of the carbon atoms constituting the carbolinering is replaced with a nitrogen atom), a quinoxalinyl group, apyridazinyl group, a triazinyl group, a quinazolinyl group, and aphthalazinyl group.

The afore-mentioned groups may have a substituent represented by Y1 inFormula (1).

The groups represented by Z are preferably an aromatic hydrocarbon groupor an aromatic heterocycle.

In Formula (5), examples of an aromatic hydrocarbon which is formed byA1 with P—C include: a benzene ring, a biphenyl ring, a naphthalenering, an azulene ring, an anthracene ring, a phenanthrene ring, a pyrenering, a chrysene ring, a naphthacene ring, a triphenylene ring,o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, an acenaphthenering, a coronene ring, a fluorene ring, a fluoanthrene ring, anaphthacene ring, a pentacene ring, a perylene ring, a pentaphene ring,a picene ring, a pyrene ring, a pyranthrene ring and an anthraanthrenering.

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

In Formula (5), examples of an aromatic heterocycle which is formed byA1 with P—C include: a furan ring, a thiophene ring, an oxazole ring, apyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, apyrazine ring, a triazine ring, a benzimidazole ring, an oxadiazolering, a triazole ring, an imidazole ring, a pyrazole ring, a thiazolering, an indole ring, a benzothiazole ring, a benzoxazole ring, aquinoxaline ring, a quinazoline ring, a phthalazine ring, a carbazolering, a carboline ring and an azacarbazole ring.

An azacarbazole ring indicates a ring structure formed in such a mannerthat at least one of the carbon atoms constituting the carbazole ring isreplaced with a nitrogen atom).

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

R01 and R02 in —C(R01)═C(R02)-, —N═C(R02)- and —C(R01)═N— which arerepresented by A3 of Formula (5) indicate the same substituentrepresented by Y1 of Formula (1).

In Formula (5), examples of a bidentate ligand represented by P1-L1-P2include: phenylpyridine, phenylpyrazole, phenylimidazole,phenyltriazole, phenyltetrazole, pyrazabole, acetylacetone and picolinicacid.

In Formula (5), j1 represents an integer of 1 to 3, and j2 represents aninteger of 0 to 2, provided that a sum of j1 and j2 is 2 or 3.Especially, j2 is preferable to be 0.

In Formula (5), M1 represents a transition metal element of Groups 8 to10 of the element periodic table (it is called simply transition metal),which is the same as represented by M1 of Formula (4).

<Compound Represented by Formula (6)>

One of preferred embodiments of a compound represented by Formula (5) isa compound represented by the afore-mentioned Formula (6).

In Formula (6), R03 represents a substituent; R04 represents a hydrogenatom or a substituent; provided that a plurality of R04s may be joinedto form a ring. n01 is an integer of 1 to 4. R05 represents a hydrogenatom or a substituent; provided that a plurality of R05s may be joinedto form a ring. n02 is an integer of 1 to 2. R06 represents a hydrogenatom or a substituent; provided that a plurality of R06s may be joinedto form a ring. n03 is an integer of 1 to 4. Z1 is a group of atomsnecessary to form a 6 membered aromatic hydrocarbon ring or a 5 to 6membered aromatic heterocycle with C—C bond. Z2 is a group of atomsnecessary to form a hydrocarbon ring or a heterocycle. P1-L1-P2represents a bidentate ligand; and P1 and P2 each independentlyrepresent a carbon atom, a nitrogen atom or an oxygen atom. L1 is agroup of atoms which forms a bidentate ligand together with P1 and P2.j1 is an integer of 1 to 3; and j2 is an integer of 0 to 2, providedthat a sum of j1 and j2 is 2 or 3. M1 is a transition metal of Groups 8to 10 of the element periodic table. A pair of R03 and R06, a pair ofR04 and R06, and a pair of R05 and R06 each may be joined to form aring. In Formula (6), the substituent represented by R03, R04, R05 andR06 each indicate the same substituent represented by Y1 of Formula (1).

In Formula (6), an example of a 6 membered aromatic hydrocarbon ringwhich is formed by Z1 with C—C is preferably a benzene ring.

This ring may have a substituent represented by Y1 in Formula (1).

In Formula (6), examples of a 5 or 6 membered aromatic heterocycle whichis formed by Z1 with C—C bond include: an oxazole ring, an oxadiazolering, a oxatriazole ring, an isoxazole ring, a tetrazole ring, athiadiazole ring, a thiatriazole ring, an isothiazole ring, a thiophenering, a furan ring, a pyrrole ring, a pyridine ring, a pyridazine ring,a pyrimidine ring, a pyrazine ring, a triazine ring, an imidazole ring,a pyrazole ring and a triazole ring.

The afore-mentioned rings may have a substituent represented by Y1 inFormula (1).

In Formula (6), examples of a hydrocarbon ring group represented by Z2include a non-aromatic hydrocarbon ring group and an aromatichydrocarbon ring group. Examples of a non-aromatic hydrocarbon ringgroup include: a cyclopropyl group, a cyclopentyl group and a cyclohexylgroup. These groups may be unsubstituted or may be substituted with asubstituent which will be described subsequently.

Examples of an aromatic hydrocarbon ring group (it is also called as anaryl group) include: a phenyl group, p-chlorophenyl group, a mesitylgroup, a tolyl group, a xylyl group, a naphthyl group, a anthryl group,an azulenyl group, a acenaphthenyl group, a fluorenyl group, aphenanthryl group, an indenyl group, a pyrenyl group and a biphenylgroup. The afore-mentioned groups may be unsubstituted or have asubstituent represented by Y1 in Formula (1).

In Formula (6), examples of a heterocycle represented by Z2 include anon-aromatic heterocycle and an aromatic heterocycle. Examples of anon-aromatic heterocycle represented by Z2 include: an epoxy ring, anaziridine ring, a thiirane ring, an oxetane ring, an azetidine ring, athietane ring, a tetrahydrofuran ring, a dioxorane ring, a pyrrolidinering, a pyrazolidine ring, a imidazolidine ring, a oxazolidine ring, atetrahydrothiophene ring, the sulforane ring, a thiazolidine ring,□-caprolactone ring, □-caprolactam ring, a piperidine ring, ahexahydropyridazine ring, a hexahydropyrimidine ring, a piperazine ring,a morpholine ring, a tetrahydropyrane ring, a 1,3-dioxane ring, a1,4-dioxane ring, a trioxane ring, a tetrahydrothiopyrane ring, athiomorpholine ring, a thiomorpholine-1,1-dioxide ring, a pyranose ringand a diazabicyclo[2,2,2]-octane ring. The afore-mentioned groups may beunsubstituted or have a substituent represented by Y1 in Formula (1).

Examples of an aromatic heterocycle represented by Z include: a pyridylgroup, a pyrimidinyl group, a furyl group, a pyrrolyl group, animidazolyl group, a benzimidazolyl group, a pyrrazolyl group, apyradinyl group, a triazolyl group (for example, 1,2,4-triazole-1-ylgroup, 1,2,3-triazole-1-yl group, etc.), an oxazolyl group, abenzoxazolyl group, a thiazolyl group, an isooxazolyl group, anisothiazolyl group, a furazanyl group, a thienyl group, a quinolylgroup, a benzofuryl group, a dibenzofuryl group, a benzothienyl group, adibenzothienyl group, an indolyl group, a carbazolyl group, a carbolinylgroup, a diazacarbazolyl group (indicating a ring structure formed insuch a manner that one of the carbon atoms constituting the carbolinering is replaced with a nitrogen atom), a quinoxalinyl group, apyridazinyl group, a triazinyl group, a quinazolinyl group, and aphthalazinyl group.

The afore-mentioned groups may be unsubstituted or have a substituentrepresented by Y1 in Formula (1).

In Formula (6), an example of a group which is formed by Z1 with Z2 ispreferably a benzene ring.

In Formula (6), a bidentate ligand represented by P1-L1-P2 indicates thesame bidentate ligand as indicated by P1-L1-P2 of Formula (4).

In Formula (6), M1 represents a transition metal element of Groups 8 to10 of the element periodic table, which is the same as represented by M1of Formula (4).

A phosphorescence emitting compound can be suitably selected from theknown phosphorescence emitting compounds used in the light emittinglayer of an organic EL element.

A phosphorescence emitting compound of the present invention ispreferably a transition metal complex compound containing a transitionmetal of Groups 8 to 10 of the element periodic table. More preferabletransition metal complexes are an iridium compound, an osmium compoundand a platinum compound (a platinum complex compound) and a rare-earthcomplex. Among them, a most preferably compound is an iridium compound.

Examples of a phosphorescence emitting compound of the present inventionare shown below, however, the present invention is not limited to them.

The phosphorescence-emitting compound of the present invention can besynthesized by applying a method described in such as Organic Letter,vol. 3, No. 16, pp. 2579-2581 (2001), Inorganic Chemistry, vol. 30, No.8, pp. 1685-1687 (1991), J. Am. Chem. Soc., vol. 123, p. 4304 (2001),Inorganic Chemistry, vol. 40, No. 7, pp. 1704-1711 (2001), InorganicChemistry, vol. 41, No. 12, pp. 3055-3066 (2002), New Journal ofChemistry, vol. 26, p. 1171 (2002), European Journal of OrganicChemistry, vol. 4, pp. 695-709 (2004), and reference documents describedin these documents.

(Fluorescent Dopants (Also Referred to as Fluorescent Compounds))

As fluorescent dopants, listed are coumarin based dyes, pyran baseddyes, cyanine based dyes, croconium based dyes, squarylium based dyes,oxobenzanthracene based dyes, fluorescein based dyes, Rhodamine baseddyes, pyrylium based dyes, perylene based dyes, stilbene based dyes,polythiophene based dyes, or rare earth complex based fluorescentmaterials.

An injection layer and an inhibition layer, used for an electrontransport layer of a constituting layer of the organic EL element of thepresent invention will now be described.

<Injection Layer: Electron Injection Layer, Positive Hole InjectionLayer>

An injection layer is appropriately provided and includes an electroninjection layer and a positive hole injection layer, which may bearranged between an anode and a light emitting layer or a positivetransfer layer, and between a cathode and a light emitting layer or anelectron transport layer, as described above.

An injection layer is a layer which is arranged between an electrode andan organic layer to decrease an operating voltage and to improve anemission luminance, which is detailed in volume 2, chapter 2 (pp.123-166) of “Organic EL Elements and Industrialization Front thereof(Nov. 30, 1998, published by N. T. S Corp.)”, and includes a positivehole injection layer (an anode buffer layer) and an electron injectionlayer (a cathode buffer layer).

An anode buffer layer (a positive hole injection layer) is also detailedin such as JP-A 9-45479, 9-260062 and 8-288069, and specific examplesinclude such as a phthalocyanine buffer layer comprising such as copperphthalocyanine, an oxide buffer layer comprising such as vanadium oxide,an amorphous carbon buffer layer, and a polymer buffer layer employingconductive polymer such as polythiophene.

A cathode buffer layer (an electron injection layer) is also detailed insuch as JP-A 6-325871, 9-17574 and 10-74586, and specific examplesinclude a metal buffer layer comprising such as strontium and aluminum,an alkali metal compound buffer layer comprising such as lithiumfluoride, an alkali earth metal compound buffer layer comprising such asmagnesium fluoride, and an oxide buffer layer comprising such asaluminum oxide. The above-described buffer layer (injection layer) ispreferably a very thin layer, and the layer thickness is preferably in arange of 0.1-100 nm although it depends on a raw material.

<Inhibition Layer: Positive Hole Inhibition Layer, Electron InhibitionLayer>

An inhibition layer is appropriately provided in addition to the basicconstitution layers composed of organic thin layers as described above.Examples are described in such as JP-A Nos. 11-204258 and 11-204359 andp. 273 of “Organic EL Elements and Industrialization Front Thereof (Nov.30 (1998), published by N.T.S Corp.)” is applicable to a positive holeinhibition (hole block) layer according to the present invention.

A positive hole inhibition layer, in a broad meaning, is provided with afunction of electron transport layer, being comprised of a materialhaving a function of transporting an electron but a very small abilityof transporting a positive hole, and can improve the recombinationprobability of an electron and a positive hole by inhibiting a positivehole while transporting an electron.

Further, a constitution of an electron transport layer described latercan be appropriately utilized as a positive hole inhibition layeraccording to the present invention.

The positive hole inhibition layer of the organic EL element of thepresent invention is preferably arranged adjacent to the light emittinglayer.

It is preferable that the positive hole inhibition layer incorporates acarbazole derivative, a carboline derivative or a diazacarbazolederivative (indicating a ring structure formed in such a manner that oneof the carbon atoms constituting the carboline ring is replaced with anitrogen atom) listed as a host compound.

Further, in the present intention, in the case in which a plurality oflight emitting layers which differ in a plurality of different emittedlight colors, it is preferable that the light emitting layer whichresults in the shortest wavelength of the emitted light maximumwavelength is nearest to the anode in all light emitting layers.However, in such a case, it is preferable to additionally arrange thepositive hole inhibition layer between the aforesaid shortest wavelengthlayer and the light emitting layer secondly near the anode. Further, atleast 50% by weight of the compounds incorporated in the positive holeinhibition layer arranged in the aforesaid position preferably exhibitsthe ionization potential which is greater by at least 0.3 eV than thatof the host compounds of the aforesaid shortest wavelength lightemitting layer.

The ionization potential is defined as energy which is necessary torelease electrons in the HOMO (being the highest occupied molecularorbital) to the vacuum level, and may be determined via, for example,the method described below.

(1) By employing Gaussian98 (Gauaaian98, Revision A. 11. 4, M. J.Frisch, et al. Gaussian 98 (Gaussian98, Revision A. 11. 4, M. J. Frisch,et al, Gaussian, Inc., Pittsburgh Pa., 2002), which is a molecularorbital calculation software, produced by Gaussian Co. in the UnitedState of America, and by employing B3LYP/6-31G* as a key word, the value(in terms of corresponding eV unit) was computed, and it is possible toobtain the ionization potential by rouging off the second decimal point.The background, in which the resulting calculated values are effective,is that the calculated values obtained by the above method exhibit highrelationship with the experimental values.

(2) It is possible to determine the ionization potential via a method inwhich ionization potential is directly determined employing aphotoelectron spectrometry. For example, by employing a low energyelectron spectrophotometer “Model AC-1”, produced by Riken Keiki Co., orappropriately employ a method known as an ultraviolet light electronspectrometry.

It may be possible to incorporate in a positive hole prohibiting layer acompound which has one of the partial structures of: a partial structurerepresented by one of Formulas (1) to (4); a partial structurerepresented by one of Formulas (5) to (8); a partial structurerepresented by one of Formulas (9) to (12); and a partial structurerepresented by one of Formulas (13) to (16).

On the other hand, the electron inhibition layer, as described herein,has a function of the positive hole transport layer in a broad sense,and is composed of materials having markedly small capability ofelectron transport, while having capability of transporting positiveholes and enables to enhance the recombination probability of electronsand positive holes by inhibiting electrons, while transportingelectrons.

Further, it is possible to employ the constitution of the positive holetransport layer, described below, as an electron inhibition layer whenneeded. The thickness of the positive hole inhibition layer and theelectron transport layer according to the present invention ispreferably 3-100 nm, but is more preferably 5-30 nm.

<Positive Hole Transport Layer>

A positive hole transport layer contains a material having a function oftransporting a positive hole, and in abroad meaning, a positive holeinjection layer and an electron inhibition layer are also included in apositive hole transport layer. A single layer of or plural layers of apositive hole transport layer may be provided.

A positive hole transport material is those having any one of a propertyto inject or transport a positive hole or a barrier property to anelectron, and may be either an organic substance or an inorganicsubstance. For example, listed are a triazole derivative, an oxadiazolederivative, an imidazole derivative, a polyarylalkane derivative, apyrazolone derivative, a phenylenediamine derivative, an arylaminederivative, an amino substituted chalcone derivative, an oxazolederivatives, a styrylanthracene derivative, a fluorenone derivative, ahydrazone derivative, a stilbene derivative, a silazane derivative, ananiline type copolymer, or conductive polymer oligomer and specificallypreferably such as thiophene oligomer.

As a positive hole transport material, those described above can beutilized, however, it is preferable to utilized a porphyrin compound, anaromatic tertiary amine compound and a styrylamine compound, andspecifically preferably an aromatic tertiary amine compound.

Typical examples of an aromatic tertiary amine compound and astyrylamine compound include N,N,N′,N′-tetraphenyl-4,4′-diaminophenyl;N,N′-diphenyl-N,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine(TDP); 2,2-bis(4-di-p-tolylaminophenyl)propane;1,1-bis(4-di-p-tolylaminophenyl)cyclohexane; N,N,N′,N′-tetra-p-tolyl4,4′-diaminobiphenyl;1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;bis(4-dimethylamino-2-methyl)phenylmethane;bis(4-di-p-tolylaminophenyl)phenylmethane;N,N′-diphenyl-N,N′-di(4-methoxyphenyl)-4,4′-diaminobiphenyl;N,N,N′,N′-tetraphenyl-4,4′-diaminophenylether;4,4′-bis(diphenylamino)quadriphenyl; N,N,N-tri(p-tolyl)amine;4-(di-p-tolylamino)-4′-[4-(di-p-triamino)styryl]stilbene;4-N,N-diphenylamino-(2-diphenylvinyl)benzene;3-methoxy-4′-N,N-diphenylaminostilbene; and N-phenylcarbazole, inaddition to those having two condensed aromatic rings in a moleculedescribed in U.S. Pat. No. 5,061,569, such as4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NDP), and4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine (MDTDATA),in which three of triphenylamine units are bonded in a star burst form,described in JP-A 4-308688.

Polymer materials, in which these materials are introduced in a polymerchain or constitute the backbone of polymer, can be also utilized.Further, an inorganic compound such as a p type-Si and a p type-SiC canbe utilized as a positive hole injection material and a positive holetransport material

Further, it is possible to employ so-called p type positive holetransport materials, as described in Japanese Patent Publication Open toPublic Inspection (hereinafter referred to as JP-A) No. 11-251067, andJ. Huang et al. reference (Applied Physics Letters 80 (2002), p. 139).In the present invention, since high efficiency light emitting elementsare prepared, it is preferable to employ these materials.

This positive hole transport layer can be prepared by forming a thinlayer made of the above-described positive hole transport materialaccording to a method well known in the art such as a vacuum evaporationmethod, a spin coating method, a cast method, an inkjet method and a LBmethod. The layer thickness of a positive hole transport layer is notspecifically limited, however, it is generally 5 nm-5 □m, and preferably5 nm-200 nm. This positive transport layer may have a single layerstructure comprised of one or not less than two types of the abovedescribed materials.

Further, it is possible to employ a positive hole transport layer of ahigher p property which is doped with impurities. As its example, listedare those described in each of JP-A Nos. 4-297076, 2000-196140,2001-102175, as well as in J. Appl. Phys., 95,5773 (2004).

In the present invention, it is preferable to employ a positive holetransport layer of such a high p property, since it is possible toproduce an element of lower electric power consumption.

<Anode>

As an anode according to an organic EL element of the present invention,those comprising metal, alloy, a conductive compound, which is providedwith a large work function (not less than 4 eV), and a mixture thereofas an electrode substance are preferably utilized. Specific examples ofsuch an electrode substance include a conductive transparent materialsuch as metal like Au, CuI, indium tin oxide (ITO), SnO2 and ZnO.

Further, a material such as IDIXO (In2O3-ZnO), which can prepare anamorphous and transparent electrode, may be also utilized. As for ananode, these electrode substances may be made into a thin layer by amethod such as evaporation or spattering and a pattern of a desired formmay be formed by means of photolithography, or in the case ofrequirement of pattern precision is not so severe (not less than 100□m), a pattern may be formed through a mask of a desired form at thetime of evaporation or spattering of the above-described substance.

Alternatively, when coatable materials such as organic electricallyconductive compounds are employed, it is possible to employ a wet systemfilming method such as a printing system or a coating system. Whenemission is taken out of this anode, the transmittance is preferably setto not less than 10% and the sheet resistance as an anode is preferablynot more than a few hundreds □/□. Further, although the layer thicknessdepends on a material, it is generally selected in a range of 10-1,000nm and preferably of 10-200 nm.

<Cathode>

On the other hand, as a cathode according to the present invention,metal, alloy, a conductive compound and a mixture thereof, which have asmall work function (not more than 4 eV), are utilized as an electrodesubstance. Specific examples of such an electrode substance includessuch as sodium, sodium-potassium alloy, magnesium, lithium, amagnesium/copper mixture, a magnesium/silver mixture, amagnesium/aluminum mixture, a magnesium/indium mixture, analuminum/aluminum oxide (Al2O3) mixture, indium, a lithium/aluminummixture and rare earth metal. Among them, with respect to an electroninjection property and durability against such as oxidation, preferableare a mixture of electron injecting metal with the second metal which isstable metal having a work function larger than electron injectingmetal, such as a magnesium/silver mixture, a magnesium/aluminum mixture,a magnesium/indium mixture, an aluminum/aluminum oxide (Al2O3) mixtureand a lithium/aluminum mixture, and aluminum.

As for a cathode, these electrode substances may be made into a thinlayer by a method such as evaporation or spattering. Further, the sheetresistance as a cathode is preferably not more than a few hundreds □/□and the layer thickness is generally selected in a range of 10-1,000 nmand preferably of 10-200 nm. Herein, to transmit emission, either one ofan anode or a cathode of an organic EL element is preferably transparentor translucent to improve the mission luminance.

Further, after forming, on the cathode, the above metals at a filmthickness of 1-20 nm, it is possible to prepare a transparent ortranslucent cathode in such a manner that electrically conductivetransparent materials are prepared thereon. By applying the above, it ispossible to produce an element in which both anode and cathode aretransparent.

<Substrate>

A substrate according to an organic EL element of the present inventionis not specifically limited with respect to types of such as glass andplastics. They may be transparent or opaque. However, a transparentsubstrate is preferable when the emitting light is taken from the sideof substrate. Substrates preferably utilized includes such as glass,quartz and transparent resin film. A specifically preferable substrateis resin film capable of providing an organic EL element with a flexibleproperty.

Resin film includes such as: polyesters such as polyethyleneterephthalate (PET) and polyethylene naphthalate (PEN); polyethylene,polypropyrene; cellulose esters or their derivatives such as cellophane,cellulose diacetate, cellulose triacetate, cellulose acetate butylate,cellulose acetate propionate (CAP), cellulose acetate phthalate (TAC)and cellulose nitrate; polyvinylidene chloride, polyvinyl alcohol,polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate,norbornene resin, polymethylpentene, polyether ketone, polyimide,polyether sulfone (PES), polyphenylene sulfide, polysulfones,polyetherimide, polyether ketone imide, polyamide, fluororesin, Nylon,polymethylmethacrylate, acrylic resin, polyacrylate; and cycloolefineresins such as ARTON (produced by JSR Co. Ltd.) and APEL (produce byMitsui Chemicals, Inc.)

On the surface of a resin film, formed may be a film incorporatinginorganic and organic compounds or a hybrid film of both. Barrier filmsare preferred at a water vapor permeability (25±0.5° C., and relativehumidity (90±2) % RH) of at most 0.01 g/(m2·24 h), determined based onJIS K 7129-1992. Further, high barrier films are preferred at an oxygenpermeability of at most 1×10-3 ml/(m2·24 h·MPa), and at a water vaporpermeability of at most 10-5 g/(m2·24 h), determined based on JIS K7126-1987.

As materials forming a barrier film, employed may be those which retardpenetration of moisture and oxygen, which deteriorate the element. Forexample, it is possible to employ silicon oxide, silicon dioxide, andsilicon nitride. Further, in order to improve the brittleness of theaforesaid film, it is more preferable to achieve a laminated layerstructure of inorganic layers and organic layers. The laminating orderof the inorganic layer and the organic layer is not particularlylimited, but it is preferable that both are alternatively laminated aplurality of times.

Barrier film forming methods are not particularly limited, and examplesof employable methods include a vacuum deposition method, a sputteringmethod, a reactive sputtering method, a molecular beam epitaxy method, acluster ion beam method, an ion plating method, a plasma polymerizationmethod, a plasma CVD method, a laser CVD method, a thermal CVD method,and a coating method. Of these, specifically preferred is a methodemploying an atmospheric pressure plasma polymerization method,described in JP-A No. 2004-68143.

Examples of opaque support substrates include metal plates such aluminumor stainless steel, films, opaque resin substrates, and ceramicsubstrates.

The external extraction efficiency of light emitted by the organic ELelement of the present invention is preferably at least 1% at roomtemperature, but is more preferably at least 5%.

External extraction quantum yield (%)=the number of photons emitted bythe organic EL element to the exterior/the number of electrons fed toorganic EL element

Further, it may be used simultaneously employing color hue improvingfilters such as a color filter, or color conversion filters whichconvert emitted light color from the organic EL element to multicolor byemploying fluorescent materials. When the color conversion filters areemployed, it is preferable that λmax of light emitted by the organic ELelement is at least 480 nm.

<<Sealing>>

As sealing means employed in the present invention, listed may be, forexample, a method in which sealing members, electrodes, and a supportingsubstrate are subjected to adhesion via adhesives.

The sealing members may be arranged to cover the display region of anorganic EL element, and may be an engraved plate or a flat plate.Neither transparency nor electrical insulation is limited.

Specifically listed are glass plates, polymer plate-films, metal plates,and films. Specifically, it is possible to list, as glass plates,soda-lime glass, barium-strontium containing glass, lead glass,aluminosilicate glass, borosilicate glass, bariumborosilicate glass, andquartz. Further, listed as polymer plates may be polycarbonate, acryl,polyethylene terephthalate, polyether sulfide, and polysulfone. As ametal plate, listed are those composed of at least one metal selectedfrom the group consisting of stainless steel, iron, copper, aluminummagnesium, nickel, zinc, chromium, titanium, molybdenum, silicon,germanium, and tantalum, or alloys thereof.

In the present invention, since it is possible to convert the element toa thin film, it is possible to preferably employ a polymer film and ametal film.

Further, the oxygen permeability of the polymer film is preferably atmost 1×10-3 ml/(m2·24 h·MPa), determined by the method based on JIS K7126-1987, while its water vapor permeability (at 25±0.5° C. andrelative humidity (90±2) %) is at most 10-5 g/(m2·24 h), determined bythe method based on JIS K 7129-1992.

Conversion of the sealing member into concave is carried out employing asand blast process or a chemical etching process.

In practice, as adhesives, listed may be photo-curing and heat-curingtypes having a reactive vinyl group of acrylic acid based oligomers andmethacrylic acid, as well as moisture curing types such as2-cyanoacrylates.

Further listed may be thermal and chemical curing types (mixtures of twoliquids) such as epoxy based ones. Still further listed may be hot-melttype polyamides, polyesters, and polyolefins. Yet further listed may becationically curable type ultraviolet radiation curable type epoxy resinadhesives.

In addition, since an organic EL element is occasionally deterioratedvia a thermal process, those are preferred which enable adhesion andcuring between room temperature and 80° C. Further, desiccating agentsmay be dispersed into the aforesaid adhesives.

Adhesives may be applied onto sealing portions via a commercialdispenser or printed on the same in the same manner as screen printing.

Further, it is appropriate that on the outside of the aforesaidelectrode which interposes the organic layer and faces the supportsubstrate, the aforesaid electrode and organic layer are covered, and inthe form of contact with the support substrate, inorganic and organicmaterial layers are formed as a sealing film. In this case, as materialsforming the aforesaid film may be those which exhibit functions toretard penetration of those such as moisture or oxygen which results indeterioration. For example, it is possible to employ silicon oxide,silicon dioxide, and silicon nitride.

Still further, in order to improve brittleness of the aforesaid film, itis preferable that a laminated layer structure is formed, which iscomposed of these inorganic layers and layers composed of organicmaterials.

Methods to form these films are not particularly limited. It is possibleto employ, for example, a vacuum deposition method, a sputtering method,a reactive sputtering method, a molecular beam epitaxy method, a clusterion beam method, an ion plating method, a plasma polymerization method,an atmospheric pressure plasma polymerization method, a plasma CVDmethod, a thermal CVD method, and a coating method.

In a gas phase and a liquid phase, it is preferable to inject inertgases such as nitrogen or argon, and inactive liquids such asfluorinated hydrocarbon or silicone oil into the space between thesealing member and the surface region of the organic EL element.Further, it is possible to form vacuum. Still further, it is possible toenclose hygroscopic compounds in the interior.

Examples of hygroscopic compounds include metal oxides (for example,sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesiumoxide, and aluminum oxide); sulfates (for example, sodium sulfate,calcium sulfate, magnesium sulfate, and cobalt sulfate); metal halides(for example, calcium chloride, magnesium chloride, cesium fluoride,tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, andmagnesium iodide); perchlorates (for example, barium perchlorate andmagnesium perchlorate). In sulfates, metal halides, and perchlorates,suitably employed are anhydrides.

<<Protective Film and Protective Plate>>

The aforesaid sealing film on the side which nips the organic layer andfaces the support substrate or on the outside of the aforesaid sealingfilm, a protective or a protective plate may be arranged to enhance themechanical strength of the element. Specifically, when sealing isachieved via the aforesaid sealing film, the resulting mechanicalstrength is not always high enough, whereby it is preferable to arrangethe protective film or the protective plate described above. Usablematerials for these include glass plates, polymer plate-films, and metalplate-films which are similar to those employed for the aforesaidsealing. However, in terms of light weight and a decrease in thickness,it is preferable to employ polymer films.

<<Light Extraction>>

It is generally known that an organic EL element emits light in theinterior of the layer exhibiting the refractive index (being about1.7-about 2.1) which is greater than that of air, whereby only about15-about 20% of light generated in the light emitting layer isextracted. This is due to the fact that light incident to an interface(being an interface of a transparent substrate to air) at an angle of θwhich is at least critical angle is not extracted to the exterior of theelement due to the resulting total reflection, or light is totallyreflected between the transparent electrode or the light emitting layerand the transparent substrate, and light is guided via the transparentelectrode or the light emitting layer, whereby light escapes in thedirection of the element side surface.

Means to enhance the efficiency of the aforesaid light extractioninclude, for example, a method in which roughness is formed on thesurface of a transparent substrate, whereby total reflection isminimized at the interface of the transparent substrate to air (U.S.Pat. No. 4,774,435), a method in which efficiency is enhanced in such amanner that a substrate results in light collection (JP-A No.63-314795), a method in which a reflection surface is formed on the sideof the element (JP-A No. 1-220394), a method in which a flat layer of amiddle refractive index is introduced between the substrate and thelight emitting body and an antireflection film is formed (JP-A No.62-172691), a method in which a flat layer of a refractive index whichis equal to or less than the substrate is introduced between thesubstrate and the light emitting body (JP-A No. 2001-202827), and amethod in which a diffraction grating is formed between the substrateand any of the layers such as the transparent electrode layer or thelight emitting layer (including between the substrate and the outside)(JP-A No. 11-283751).

In the present invention, it is possible to employ these methods whilecombined with the organic EL element of the present invention. Of these,it is possible to appropriately employ the method in which a flat layerof a refractive index which is equal to or less than the substrate isintroduced between the substrate and the light emitting body and themethod in which a diffraction grating is formed between the substrateand any of the layers such as the transparent electrode layer or thelight emitting layer (including between the substrate and the outside).

By combining these means, the present invention enables the productionof elements which exhibit higher luminance or excel in durability.

When a low refractive index medium of a thickness, which is greater thanthe wavelength of light, is formed between the transparent electrode andthe transparent substrate, the extraction efficiency of light emittedfrom the transparent electrode to the exterior increases as therefractive index of the medium decreases.

As materials of the low refractive index layer, listed are, for example,aerogel, porous silica, magnesium fluoride, and fluorine based polymers.Since the refractive index of the transparent substrate is commonlyabout 1.5-about 1.7, the refractive index of the low refractive indexlayer is preferably at most approximately 1.5, but is more preferably atmost 1.35.

Further, thickness of the low refractive index medium is preferably atleast two times the wavelength in the medium. The reason is that whenthe thickness of the low refractive index medium reaches nearly thewavelength of light so that electromagnetic waves oozed via evernescententer into the substrate, effects of the low refractive index layer arelowered.

The method in which the interface which results in total reflection or adiffraction grating is introduced in any of the media is characterizedin that light extraction efficiency is significantly enhanced. The abovemethod works as follows. By utilizing properties of the diffractiongrating capable of changing the light direction to the specificdirection different from diffraction via so-called Bragg diffractionsuch as primary diffraction or secondary diffraction of the diffractiongrating, of light emitted from the light emitting layer, light, which isnot emitted to the exterior due to total reflection between layers, isdiffracted via introduction of a diffraction grating between any layersor in a medium (in the transparent substrate and the transparentelectrode) so that light is extracted to the exterior.

It is preferable that the introduced diffraction grating exhibits atwo-dimensional periodic refractive index. The reason is as follows.Since light emitted in the light emitting layer is randomly generated toall directions, in a common one-dimensional diffraction gratingexhibiting a periodic refractive index distribution only in a certaindirection, light which travels to the specific direction is onlydiffracted, whereby light extraction efficiency is not sufficientlyenhanced.

However, by changing the refractive index distribution to atwo-dimensional one, light, which travels to all directions, isdiffracted, whereby the light extraction efficiency is enhanced.

As noted above, a position to introduce a diffraction grating may bebetween any layers or in a medium (in a transparent substrate or atransparent electrode). However, a position near the organic lightemitting layer, where light is generated, is desirous. In this case, thecycle of the diffraction grating is preferably about ½-about 3 times thewavelength of light in the medium.

The preferable arrangement of the diffraction grating is such that thearrangement is two-dimensionally repeated in the form of a squarelattice, a triangular lattice, or a honeycomb lattice.

<<Light Collection Sheet>>

Via a process to arrange a structure such as a micro-lens array shape onthe light extraction side of the organic EL element of the presentinvention or via combination with a so-called light collection sheet,light is collected in the specific direction such as the front directionwith respect to the light emitting element surface, whereby it ispossible to enhance luminance in the specific direction.

In an example of the micro-lens array, square pyramids to realize a sidelength of 30 μm and an apex angle of 90 degrees are two-dimensionallyarranged on the light extraction side of the substrate. The side lengthis preferably 10-100 μm. When it is less than the lower limit,coloration results due to generation of diffraction effects, while whenit exceeds the upper limit, the thickness increases undesirably.

It is possible to employ, as a light collection sheet, for example, onewhich is put into practical use in the LED backlight of liquid crystaldisplay devices. It is possible to employ, as such a sheet, for example,the luminance enhancing film (BEF), produced by Sumitomo 3M Limited.

As shapes of a prism sheet employed may be, for example, Δ shapedstripes of an apex angle of 90 degrees and a pitch of 50 μm formed on abase material, a shape in which the apex angle is rounded, a shape inwhich the pitch is randomly changed, and other shapes.

Further, in order to control the light radiation angle from the lightemitting element, simultaneously employed may be a light diffusionplate-film. For example, it is possible to employ the diffusion film(LIGHT-UP), produced by Kimoto Co., Ltd.

<<Preparation Method of Organic EL Element>>

As one example of the preparation method of the organic EL element ofthe present invention, the preparation method of the organic EL elementcomposed of “anode/positive hole injection layer/positive hole transportlayer/light emitting layer/positive hole inhibiting layer/electrontransport layer/cathode buffer layer/cathode” will be described.

Initially, a thin film composed of desired electrode substances, forexample, anode substances is formed on an appropriate base material toreach a thickness of at most 1 μm but preferably 10-200 nm, employing amethod such as vapor deposition or sputtering, whereby an anode isprepared. Subsequently, on the above, formed are organic compound thinlayers including a positive hole injection layer, a positive holetransport layer, a light emitting layer, a positive hole inhibitionlayer, an electron transport layer, and an electron injection layer,which are organic EL element materials.

Methods to form each of these layers include, as described above, a spincoating method, a cast method, an ink-jet method, a vapor depositionmethod and a printing method. In view of easy formation of a homogeneousfilm and rare formation of pin holes, preferred coating methods are thespin coating method and the vapor deposition method. Different coatingmethods may be applied for different layers.

When a vapor deposition method is adopted for making a layer, thecondition of a vapor deposition varies depending on the compoundsemployed. It is generally preferable to select the conditions of:heating temperature of a boat, 50 to 450° C.; vacuum degree, 10-6 to10-2 Pa; deposition rate, 0.01 to 50 nm/sec; temperature of a substrate,−50 to 300° C.; and layer thickness, 0.1 to 5 □m.

After forming these layers, a thin layer composed of cathode materialsis formed on the above layers via a method such as vapor deposition orsputtering so that the film thickness reaches at most 1 μm, but ispreferably in the range of 50-200 nm, whereby a cathode is arranged, andthe desired organic EL element is prepared.

Further, by reversing the preparation order, it is possible to achievepreparation in order of a cathode, a cathode buffer layer, an electrontransport layer, a positive hole prohibiting layer, a light emittinglayer, a positive hole transport layer, a positive hole injection layer,and an anode.

When direct current voltage is applied to the multicolor display deviceprepared as above, the anode is employed as + polarity, while thecathode is employed as − polarity. When 2-40 V is applied, it ispossible to observe light emission. Further, alternating current voltagemay be applied. The wave form of applied alternating current voltage isnot specified.

When an organic EL element of the present invention is prepared, it ispreferred to make all of the layers from a cathode layer to a positivehole injection layers without interruption and with one time evacuation.However, it may be possible to take out the intermediate product and mayapply it a different layer making process. For that purpose, it isrequired to carry out the operation under a dry inert gas atmosphere.

<<Application>>

It is possible to employ the organic EL element of the present inventionas display devices, displays, and various types of light emittingsources. Examples of light emitting sources include, but are not limitedto lighting apparatuses (home lighting and car lighting), clocks,backlights for liquid crystals, sign advertisements, signals, lightsources of light memory media, light sources of electrophotographiccopiers, light sources of light communication processors, and lightsources of light sensors. It is effectively employed especially asbacklights of liquid crystal display devices and lighting sources.

If needed, the organic EL element of the present invention may undergopatterning via a metal mask or an ink-jet printing method during filmformation. When the patterning is carried out, only an electrode mayundergo patterning, an electrode and a light emitting layer may undergopatterning, or all element layers may undergo patterning. Duringpreparation of the element, it is possible to employ conventionalmethods.

Color of light emitted by the organic EL element of the presentinvention and compounds according to the present invention is specifiedas follows. In FIG. 4.16 on page 108 of “Shinpen Shikisai KagakuHandbook (New Edition Color Science Handbook)” (edited by The ColorScience Association of Japan, Tokyo Daigaku Shuppan Kai, 1985), valuesdetermined via a spectroradiometric luminance meter CS-1000 (produced byKonica Minolta Sensing Inc.) are applied to the CIE chromaticitycoordinate, whereby the color is specified. Further, when the organic ELelement of the present invention is a white element, “white”, asdescribed herein, means that when 2-degree viewing angle front luminanceis determined via the aforesaid method, the color temperature at1000cd/m2 is in the range of 7000 to 2500 K (the deviation from blackbody locus □uv=±0.02).

<<Display Device>>

The display device of the present invention will now be described.

The display device of the present invention incorporates the organic ELelements of the present invention.

The constitution of the organic EL element incorporated in the displaydevice is selected from constitutional examples of the aforesaid organicEL element.

Further, the manufacturing method of the organic EL element is one whichhas been shown in one embodiment of manufacturing the aforesaid organicEL element of the present invention.

When direct current voltage is applied to the resulting display device,it is possible to observe light emission via application of a voltage of2-40 V, while the polarity of the anode is “+” and the polarity of thecathode is “−”. Further, when reverse polarity voltage is applied, noelectric current flows, and no light emission results. Still further,when alternating current voltage is applied, light emission results onlyin a state in which the polarity of the anode is “+” and the polarity ofthe cathode is “−”. Incidentally, any waveform of applied alternatingcurrent is feasible.

Display devices are employable as a display device, a display, andvarious light emitting light sources. Such display devices and displaysinclude television, personal computers, mobile equipment, AV equipment,teletext displays, and vehicular information displays. Specifically, itmay be employed as a display device reproducing still and moving images.The drive system when employed as a display device for moving-imagereproduction may be either a simple matrix (a passive matrix) system oran active matrix system.

Light emitting light sources include home lighting, car interiorlighting, backlight for watches and liquid crystals, advertisingdisplays, traffic lights, light sources for light memory media, lightsources for electrophotographic copiers, light sources for lightcommunication processors, and light sources for light sensors, howeverthe present invention is not limited to only these.

One example of a display device, incorporating the organic EL element ofthe present invention, will now be described with reference to figures.

FIG. 1 is a schematic view showing one example of a display device whichis composed of an organic EL element. It is a schematic view of adisplay, such as a cellular telephone display, which displays imageinformation via light emission of an organic EL element.

Display 1 is composed of display section A having a plurality of pixelsand control section B which conducts image scanning based on imageinformation.

Control section B is electrically connected to display section A.Scanning signals and image data signals are transmitted to each of theplural pixels based on the image information from the exterior, and thepixels of each scanning line sequentially emit light via the scanningsignals depending on image data signals, followed by image scanning,whereby image information is displayed on display section A.

FIG. 2 is a schematic view of display section A. Display section Aincorporates, a wiring section incorporating plural scanning lines 5 anddata lines 6 as well as plural pixels 3 on the substrate. The majormember of display section A will now be described.

In FIG. 2, shown is a case in which light emitted by pixel 3 isextracted in the white arrow direction (the downward direction).

Scanning lines 5 and plural data lines 6 are each composed ofelectrically conductive materials and scanning lines 5 and data lines 6are orthogonally arranged in a lattice and connected to pixel 3 in theorthogonally arranged position (not shown in detail). When scanningsignals are applied to pixels 3 from scanning lines 5, pixels 3 receiveimage data signals from data lines 6, followed by light emissiondepending on the receiving image data.

By appropriately arranging parallel pixels emitting light in the redregion, in the green region, and in the blue region, it is possible toachieve a full-color display.

The light emitting process will now be described.

FIG. 3 is a schematic view of a pixel. The pixel incorporates organic ELelement 10, switching transistor 11, drive transistor 12, and condenser13. As organic EL element 10, red, green, and blue light emittingorganic EL elements are employed in a plurality of pixels. It ispossible to achieve a full-color display by arranging parallel these onthe same substrate.

In FIG. 3, image data signals are applied to the drain of switchingtransistor 11 via data lines 6 from control section B. Subsequently,when scanning signals are applied to the gate of switching transistor 11via scanning lines 5 from control section B, the drive of switchingtransistor 11 is activated, and image data signals applied to the drainare transmitted to the gate of condenser 13 and drive transistor 12.

Via transmission of image data signals, condenser 13 is chargeddepending on the electric potential of the image data signals, andsimultaneously, drive of drive transistor 12 is activated. In drivetransistor 12, the drain is connected to power source line 7, and thesource is connected to the electrode of organic EL element 10, and anelectric current is fed to organic EL element 10 from power source line7, depending on the electric potential of the image data signals appliedto the gate.

When scanning signals are transferred to the following scanning lines 5via sequential scanning of control section B, drive of switchingtransistor 11 is deactivated. However, even though the drive ofswitching transistor 11 is activated, condenser 13 maintains theelectric potential of charged image data signals, whereby the drive ofdrive transistor 12 is maintained in an on-state and light emission oforganic EL element 10 continues until the following scanning signals areapplied. When the following scanning signals are applied via sequentialscanning, drive transistor 12 is driven depending on the electricpotential of the following image data signals synchronized with scanningsignals, whereby organic EL element 10 emits light.

Namely, light emission of organic EL element 10 is carried out in such amanner that switching transistor 11, which is an active element, anddrive transistor 12 are arranged in organic EL element 10 of each of theplural pixels and organic EL element 10 of each of the plural pixels 3emits light. The aforesaid light emitting method is called an activematrix system.

Light emission of organic EL element 10 may be light emission at aplurality of gradations via multi-valued image data having a pluralityof gradation potentials or may be on and off of specified light emittingamount via binary image data signals. Further, the electric potential ofcondenser 13 may be maintained until application of the next scanningsignals, or discharge may be carried out immediately prior toapplication of the next scanning signals.

The present invention is not limited to the aforesaid active matrixsystem. The light emission drive of a passive matrix system is alsofeasible, in which an organic EL element emits light based on datasignals only when scanning signals are scanned.

FIG. 4 is a schematic view of a display device based on the passivematrix system. In FIG. 4, plural scanning lines 5 and plural image datalines 6 are arranged to form a lattice while sandwiching pixel 3. Whenscanning signals of scanning lines 5 are applied via sequentialscanning, pixels 3 connected to applied scanning lines 5 emit lightbased on image data signals.

In the passive matrix system, no active element is incorporated toeffect decreased production cost.

<<Lighting Devices>>

Lighting devices of the present invention will now be described. Thelighting devices of the present invention incorporate the aforesaidorganic EL element.

The organic EL element of the present invention may be employed as onehaving a resonator structure. Intended uses of the aforesaid organic ELelement having the resonator structure include, but are not limited to,light sources for light memory media, light sources forelectrophotographic copiers, light sources for light communicationprocessors, and light sources for light sensors. Further, via laseroscillation, it may be employed for the aforesaid uses.

Further, the organic EL element of the present invention may be employedas a type of lamp for lighting or an exposure light source, a projectiondevice such a type of projecting images, and a still image and movingimage directly viewing type display device (a display).

A drive system employed as a moving image reproducing display device maybe either a simple matrix (a passive matrix) system or an active matrixsystem. Alternatively, by employing at least two types of the organic ELelements of the present invention having different emitted light colors,it is possible to produce a full-color display device.

Further, the organic EL materials of the present invention may beapplied to an organic EL element which substantially emits white light.White light emission is obtained via simultaneous emission of aplurality of colors via a plurality of light emitting materials.Combinations of a plurality of such emitted light colors may includethree emitted light maximum wavelengths of the three primary colors ofblue, green, and red, or may include two emitted light maximumwavelengths utilizing the complementary color relationship such as blueand yellow or bluish-green and orange.

Further, combinations of light emitting materials to obtain a pluralityof emitted light colors include any of the combinations in which aplurality of phosphorescence or fluorescence emitting materials iscombined or in which light emitting materials emitting fluorescence orphosphorescence and dye materials, which emit light as excited lightfrom light emitting materials, are combined. However, in the whiteorganic EL elements according to the present invention, it is sufficientthat only a plurality of light emitting dopants is combined.

It is sufficient that during formation of a light emitting layer, apositive hole transport layer or an electron transport layer, a mask isarranged and a simple arrangement such as coated separation via the maskis carried out. The other layers require no common patterning such as amask, and for example, an electrode film can be formed on one side via avacuum deposition method, a casting method, a spin coating method anink-jet method, or a printing method, whereby productivity is enhanced.

According to this method, the element itself emits white light,differing from the white organic EL device in which light emittingelements emitting a plurality of colors are paralleled to form an array.

Materials employed in the light emitting layer are not particularlylimited. For example, with regard to a backlight in a liquid crystaldisplay element, white may be realized by selecting and combining any ofthe metal complexes according to the present invention or prior artlight emitting materials to match with the wavelength regioncorresponding to CF (color filter) characteristics.

<<One Embodiment of Lighting Device of Present Invention>>

One embodiment of the lighting device incorporating the organic ELelement of the present invention will now be described.

The non-light emitting surface of the organic EL element of the presentinvention is covered with a glass case, and a 300 μm thick glasssubstrate is employed as a sealing substrate. As a sealing material, anepoxy based light curable type adhesive (LUXTRACK LC0629B produced byToagosei Co., Ltd.) is applied to the periphery, and the resultingproduct is superposed onto the cathode to be brought into close contactwith the transparent supporting substrate, followed by curing byexposing the glass substrate side to UV radiation and sealing, wherebyit is possible to form the lighting devices, shown in FIGS. 5 and 6.

FIG. 5 is a schematic view of a lighting device. Organic EL element 101of the present invention is covered with glass cover 102 (incidentally,sealing via the glass cover was carried out in a glove box (in anambience of high purity nitrogen gas of a purity of at least 99.999%)under nitrogen ambience) without allowing contact of organic EL element101 with the ambient atmosphere).

FIG. 6 is a cross-sectional view of the lighting device. In FIG. 6, 105represents a cathode, 106 represents an organic EL layer, and 107represents a glass substrate incorporating a transparent electrode.

The interior of glass cover 102 is filled with nitrogen gas 108, andwater catching agent 109 is provided.

EXAMPLES

The present invention will now be described with reference to examples,however the present invention is not limited thereto. Further,structures of the compounds employed in the following examples are shownbelow.

Example 1 Preparation of Organic EL Element 1-1

After carrying out patterning onto a substrate (NA-45 produced by NHTechno Glass Corp.) having thereon a 150 nm ITO film as an anode, theabove transparent supporting substrate arranged with the ITO transparentelectrode was subjected to ultrasonic washing with iso-propyl alcohol,and was dried via desiccated nitrogen gas, followed by UV ozone cleaningfor 5 minutes.

The aforesaid transparent supporting substrate was fixed onto thesubstrate holder of a commercial vacuum deposition apparatus. At thesame time, each of α-NPD, H-4, Ir-12, BAlq, and Alq3 was placed in atantalum resistance heating boat and fitted to a vacuum depositionapparatus (being a first vacuum tank).

Further, lithium fluoride was placed in a tantalum resistance heatingboat and aluminum was placed in tungsten resistance boat, and both weremounted on the second vacuum tank of the vacuum deposition apparatus.

Initially, after reducing the pressure of the first vacuum tank to4×10-4 Pa, the aforesaid heating boat incorporating α-NPD waselectrically heated, and vacuum deposition was carried out onto thetransparent supporting substrate at a vacuum deposition rate of 0.1-0.2nm/second until the film thickness reached 20 nm, whereby a positivehole injection/transport layer was prepared.

Further, the aforesaid heating boats incorporating Ha and Ir-12 wereindependently electrically driven, and vacuum deposition was carried outso that the vacuum deposition rate of H4 as a light emitting host andIr-12 as a light emitting dopant was regulated to result in 100:6 toreach a film thickness of 30 nm, whereby a light emitting layer wasprepared.

Subsequently, the aforesaid heating boat incorporating BAlq waselectrically heated, and a positive hole inhibiting layer at a thicknessof 10 nm was prepared at a vacuum deposition rate of 0.1-0.2 nm/second.Further, the aforesaid heating boat incorporating Alq3 was electricallyheated, and an electron transport layer at a thickness of 10 nm wasprepared at a vacuum deposition rate of 0.1-0.2 nm/second.

Subsequently, the element, which had been subjected to film formationuntil the electron transport layer, was transferred to a second vacuumtank. Thereafter, remote control from the exterior of the apparatus wascarried out so that a stainless steel mask perforated in a rectangularshape was placed on the electron transport layer.

After the pressure of the second vacuum tank was reduced to 2×10-4 Pa, aboat incorporating lithium fluoride was electrically driven and a 0.5 nmthick cathode buffer layer was prepared at an vacuum deposition rate of0.01-0.02 nm/second. Subsequently, a boat incorporating aluminum waselectrically driven and a 150 nm thick cathode was prepared at a vacuumdeposition rate of 1-2 nm/second, whereby Organic EL Element 1-1 wasrealized.

<<Preparation of Organic EL Elements 1-2-1-7>>

Each of Organic EL Elements 1-2-1-7 was prepared in the same manner asOrganic EL Element 1-1, except that the electron transport compound inthe electron transport layer was changed from Alg₃ to each of thecompounds listed below.

<<Evaluation of Organic EL Elements 1-1-1-7>>

The resulting Organic EL Elements 1-1-1-7 were evaluated as follows.After preparation, each non-light emitting surface of the organic ELelement was covered with a glass case. A 300 μm thick glass substratewas employed as a sealing substrate, and an epoxy based light curabletype adhesive (LUXTRACK LC0629B produced by Toagosei Co., Ltd.) wasapplied to the periphery as a sealing material. The resulting productwas superposed onto the aforesaid cathode to be brought into closecontact with the aforesaid transparent supporting substrate.Subsequently, curing was carried out via exposure of UV radiation to theglass substrate side, followed by sealing, whereby the lighting devicesshown in FIGS. 5 and 6 were produced. The resulting devices were thenevaluated.

(External Extraction Quantum Efficiency)

An organic EL element was allowed to emit light at room temperature(about 23-about 25° C.) under the condition of a constant electriccurrent of 2.5 mA/cm2, and by determining emitted light luminance (L) incd/m2 immediately after lighting, external extraction quantum efficiency(η) was calculated.

The emitted light luminance was determined via CS-1000 (produced byKonica Minolta Sensing, Inc.).

The external extraction quantum efficiency was represented by a relativevalue when Organic EL Element 1 resulted in 100.

(Drive Voltage)

When organic EL elements were driven at room temperature (about 23-about25° C.) under the condition of a constant electric current of 2.5mA/cm2, the resulting voltage was respectively determined. As themeasurement results show below, each relative value is listed whenOrganic EL Element 1-1 (Comparative Example) resulted in 100.

Voltage=(drive voltage of each element/drive voltage of Organic ELElement 1-1)×100.

A smaller value indicates that the drive voltage is lower than thecomparative.

The obtained results are shown in Table 1 below.

TABLE 1 External Drive Extraction Electron Voltage Quantum ElementTransport (V) (relative Efficiency No. Compound value) (%) Remarks 1-1Alq3 100 100 Comparative Example 1-2 Comparative 91 122 ComparativeCompound 9 Example 1-3 Compound 4 80 142 Present Invention 1-4 Compound5 72 141 Present Invention 1-5 93 82 138 Present Invention 1-6 94 85 135Present Invention 1-7 95 87 129 Present Invention

As can be clearly seen from the above, organic EL elements prepared viathe compounds according to the present invention enable achievement of ahigher light emitting efficiency and a lower drive voltage, compared tocomparative organic EL elements.

Example 2 Preparation of Full-Color Display Device (Preparation of BlueLight Emitting Element)

Organic EL Element 1-4 of Example 1 was employed as a blue lightemitting element.

(Preparation of Green Light Emitting Element)

A green light emitting element was prepared in the same manner asOrganic EL Element 1-4 of Example 1, except that Ir-12 was replaced withIr-1. The resulting element was employed as a green light emittingelement.

(Preparation of Red Light Emitting Element)

A red light emitting element was prepared in the same manner as OrganicEL Element 1-4 of Example 1, except that Ir-12 was changed to Ir-9. Theresulting element was employed as a red light emitting element.

Red, green, and blue light emitting organic EL elements, prepared asabove, were arranged in parallel on the same substrate, whereby theactive matrix system full-color display device as shown in FIG. 1 wasprepared. FIG. 2 only shows the schematic view of display section of theaforesaid prepared display device.

Namely, on one substrate, incorporated are a wiring section having aplurality of scanning lines 5 and data lines 6, and a plurality ofparallel arranged pixels 3 (pixels which emit light in the red region,pixels which emit light in the green region, and pixels which emit lightin the blue region). Scanning lines 5 and a plurality of data lines 6are composed of electrically conductive materials, and scanning lines 5and data lines 6 are orthogonally arranged to form a lattice, whilethese lines are connected to each pixel 3 in the orthogonally arrangedposition (not shown in detail).

A plurality of aforesaid pixels 3 is driven via the active matrix systemin which an organic EL element corresponding to each of the emittedlight colors, and each of the switching transistors which are activeelements, and the drive transistors are arranged. When the scanningsignals from scanning lines 5 are applied, image data signals from datalines 6 are received, whereby light is emitted based on the receivedimage data. As mentioned above, by appropriately arranging red, green,and blue pixels in parallel, a full-color display device was prepared.

It was found that by driving the aforesaid full-color display device,distinct full-color moving images exhibiting high luminance and highdurability were produced.

Example 3

<<Preparation of White Light Emitting Element and White LightingDevice>>

Patterning was applied to the electrode at an area of 20 mm×20 mm of thetransparent electrode substrate of Example 1, and thereon, a 25 nm thickα-NPD film was formed as a positive hole injection/transport layer inthe same manner as Example 1. Further, the aforesaid heating boatincorporating H-4, the boat incorporating Exemplified Compound Ir-13,and the boat incorporating Ir-9 were independently electrically driven.By regulating the deposition rate of H-4 as a light emitting host aswell as Ir-13 and Ir-9 as a light emitting dopant to 100:5:0.6 until thefilm thickness reached 30 nm, whereby a light emitting layer wasprepared.

Subsequently, a 10 nm thick BAlq film was arranged to form a positivehole blocking layer. Further, a 40 nm thick Exemplified Compound 5 filmwas formed to prepare an electron transport layer.

Subsequently, in the same manner as Example 1, arranged, on the electroninjection layer, was a square perforated stainless steel mask havingalmost the same shape as the transparent electrode, and a 0.5 nm lithiumfluoride film as a cathode buffer layer and a 150 nm aluminum film as acathode were formed via vacuum deposition.

The resulting element was arranged in a sealing can via the same methodand structure as for Example 1, whereby the flat lamps, shown in FIGS. 5and 6, were produced. When the resulting lamp was electrically driven,nearly white light was emitted, and was found to be feasible as alighting device.

Example 4 Preparation of Organic EL Elements 4-1

After carrying out patterning onto a substrate (NA-45 produced by NHTechno Glass Corp.) which was prepared by forming a 100 nm ITO (indiumtin oxide) film as an anode on the aforesaid 100 mm×100 mm×1.1 mm glass,the above transparent supporting substrate, arranged with the ITOtransparent electrode, was subjected to ultrasonic wave washing withisopropyl alcohol, was dried via desiccated nitrogen gas, and then wasfurther subjected to UV ozone washing for 5 minutes.

A thin film was formed on the resulting transparent supporting substratevia a spin coating method under conditions of 3,000 rpm and 30 seconds,employing a solution prepared by dilutingpoly(3,4-ethylenedioxythiophen)-polystyrene sulfonate (PEDOT/PSS,BAYTRON P A1 4083, produced by Bayer Co.,) to 70% via pure water.Thereafter, drying was carried out at 200° C. for one hour, whereby a 20nm thick positive hole transport layer was prepared.

The resulting substrate was transferred into a nitrogen atmosphere, anda thin film was formed on the positive hole transport layer via the spincoating method, under conditions of 1,500 rpm and 30 seconds, applying asolution prepared by dissolving 50 mg of Positive Hole TransportMaterial 1 in 10 ml of toluene onto the above positive hole transportlayer. Further, ultraviolet radiation was exposed for 180 seconds tocarry out photopolymerization and cross-linkage, whereby anapproximately 20 nm thick second positive hole transport layer wasformed.

A thin film was formed on the above second positive hole transport layervia the spin coating method under conditions of 600 rpm and 30 seconds,employing a solution prepared by dissolving 100 mg of H31 and 10 mg ofIr-1 in 10 ml of toluene. Vacuum drying was carried out at 60° C. forone hour, whereby an approximately 70 nm thick light emitting layer wasformed.

Subsequently, a thin film was formed on the above light emitting layervia the spin coating method under conditions of 1,000 rpm and 30seconds, employing a solution prepared by dissolving 50 mg ofComparative Compound 1 in 10 ml of hexafluoroisopropanol (HFIP).Further, vacuum drying was carried out at 60° C. for one hour, wherebyan approximately 30 nm thick electron transport layer was formed.

Subsequently, the resulting substrate was fixed onto the substrateholder of a vacuum deposition apparatus. After reducing the pressure ofthe vacuum tank to 4×10-4 Pa, 0.4 nm lithium fluoride as a cathodebuffer layer and further 110 nm aluminum as a cathode were deposited,whereby Organic EL Element 4-1 was prepared.

<<Preparation of Organic EL Elements 4-2-4-8>>

Organic EL Elements 4-2-4-8 were prepared in the same manner as OrganicEL element 4-1, except that Comparative Compound 1 was replaced with thecompounds described below.

<<Evaluation of Organic EL Elements 4-1-4-8>>

Prepared Organic EL Elements 4-1-4-8 were evaluated as follows. Afterpreparation, the non-light emitting surface of each of the organic ELelements was covered with a glass case. An epoxy based light-curabletype adhesive (LUXTRACK LC0629B, produced by Toagosei Co., Ltd.) wasapplied as a sealing agent to the periphery of the glass cover sidewhere the glass cover was in contact with the glass substrate on whichthe organic El element was prepared. The resulting product wassuperposed onto the aforesaid cathode electrode side to be brought intoclose contact with the aforesaid transparent supporting substrate.Subsequently, curing was carried out via exposure of UV radiation to theglass substrate side, followed by sealing, whereby the lighting devicesshown in FIGS. 5 and 6 were produced. The resulting devices were thenevaluated.

Storage stability of Organic EL Elements 4-1-4-8 was evaluated via themeasurement method describe below.

(Storage Stability)

Each organic EL element was stored at 85° C. for 24 hours. Luminance ofeach prior to and after the storage was determined at a constantelectric current drive of 2.5 mA/cm2. Each luminance ratio was obtainedaccording to the following formula, and the resulting value was employedas an index of storage stability.

-   -   Storage stability (%)=luminance (2.5 mA/cm²) after        storage/luminance (2.5 mA/cm²) prior to storage

The results are listed in the following table 2.

TABLE 2 Electron Storage Element Transport Stability No. Compound (%)Remarks 4-1 Comparative 29 Comparative Compound 1 Example 4-2Comparative 46 Comparative Compound 2 Example 4-3 36 71 PresentInvention 4-4 50 75 Present Invention 4-5 25 86 Present Invention 4-6 9677 Present Invention 4-7 97 66 Present Invention 4-8 98 61 PresentInvention

As can be seen from the above, the organic EL elements of the presentinvention exhibited excellent storage stability, compared to theComparative Examples.

Example 5 Preparation of Organic EL Element 5-1

After carrying out patterning onto a substrate (NA-45 produced, by NHTechno Glass Corp.) which was prepared by forming a 100 nm ITO (indiumtin oxide) film as an anode on the aforesaid 100 mm×100 mm×1.1 mm glass,the above transparent supporting substrate arranged with the ITOtransparent electrode was subjected to ultrasonic wave washing withisopropyl alcohol, was dried via desiccated nitrogen gas, and then wassubjected to further UV ozone washing for 5 minutes.

The resulting transparent supporting substrate was fixed onto thesubstrate holder of a commercial vacuum deposition apparatus. At thesame time, 200 mg of TPD was placed in a molybdenum resistance heatingboat, 200 mg of H34 as a host compound was placed in another molybdenumresistance heating boat, Ir-25 was placed in still another molybdenumresistance heating boat, and Comparative Compound 3 was placed in stillyet another molybdenum resistance heating boat. Subsequently, all boatswere mounted onto the vacuum deposition apparatus.

Subsequently, after reducing the pressure of the vacuum tank to 4×10-4Pa, the aforesaid heating boat incorporating TPD was electricallyheated, and vacuum deposition was carried out onto the transparentsupporting substrate at a vacuum deposition rate of 0.1 nm/second,whereby a positive hole transport layer was prepared. Further, theaforesaid boats, each incorporating H34 and Ir-25, were electricallyheated, and co-vacuum deposition was carried at a vacuum deposition rateof 0.2 nm/second and 0.012 nm/second, respectively, onto the aforesaidpositive hole transport layer, whereby a light emitting layer wasprepared.

During the above vacuum deposition, the substrate was at roomtemperature. Further, the aforesaid boat incorporating ComparativeCompound 3 was electrically heated, and vacuum deposition was carriedout onto the aforesaid light emitting layer at a vacuum deposition rateof 0.1 nm/second, whereby an electron transport layer was prepared.During the above vacuum deposition, the substrate was at roomtemperature.

Further, 0.5 nm lithium fluoride and 110 nm aluminum werevacuum-deposited to form a cathode, whereby Organic EL Element 5-1 wasprepared.

<<Preparation of Organic EL Elements 5-2-5-6>>

Each of Organic EL Elements 5-2-5-6 was prepared in the same manner asOrganic EL Element 5-1, except that Comparative Compound 3 was replacedwith each of the compounds described below in Table 3.

<<Evaluation of Organic EL Elements 5-1-5-6>>

Prepared Organic EL Elements 5-1-5-6 were evaluated as follows. Each ofthem was sealed in the same manner as Organic EL Element 1, and lightingdevices shown in FIGS. 5 and 6 were formed and evaluated.

The organic EL elements prepared as above were evaluated. The resultsare shown below.

<Storage Stability>

An organic EL element was stored under conditions of 60° C. and 70%relative humidity for one month. In the same manner as Example 1,luminance of each at a constant electric current drive of 5 mA/cm2 priorto and after storage was determined. Subsequently, each luminance ratiowas obtained based on the following formula, and the resulting value wasemployed as an index of storage stability.

Storage stability (%)=luminance after storage (2.5 mA/cm2)/luminanceprior to storage (2.5 mA/cm2)×100

The results are shown below in Table 3.

TABLE 3 Electron Storage Element Transport Stability No. Compound (%)Remarks 5-1 Comparative 38 Comparative Compound 3 Example 5-2Comparative 30 Comparative Compound 4 Example 5-3 55 76 PresentInvention 5-4 99 72 Present Invention 5-5 100 65 Present Invention 5-6101 56 Present Invention

As can be seen from the above, the organic EL elements of the presentinvention exhibited excellent storage stability, compared to ComparativeExamples.

Example 6 Preparation of Organic EL Element 6-1

After carrying out patterning onto a substrate (NA-45, produced by NHTechno Glass Corp.) which was prepared by forming a 100 nm ITO (indiumtin oxide) film as an anode on the aforesaid 100 mm×100 mm×1.1 mm glass,the above transparent supporting substrate arranged with the ITOtransparent electrode was subjected to ultrasonic wave washing withisopropyl alcohol, was dried via desiccated nitrogen gas, and then wassubjected to further UV ozone washing for 5 minutes.

A thin film was formed on the resulting transparent supporting substratevia the spin coating method under conditions of 3,000 rpm and 30seconds, employing a solution prepared by dilutingpoly(3,4-ethylenedioxythiophen)-polystyrene sulfonate (PEDOT/PSS,BAYTRON P A1 4083, produced by Bayer Co.,) to 70% via pure water.Thereafter, drying was carried out at 200° C. for one hour, whereby a 20nm thick positive hole transport layer was prepared.

The resulting transparent supporting substrate was fixed onto thesubstrate holder of a commercial vacuum deposition apparatus. At thesame time, 200 mg of α-NPD was placed in a molybdenum resistance heatingboat, 200 mg of H33 as a host compound was placed in another molybdenumresistance heating boat, Ir-26 was placed in still another molybdenumresistance heating boat, and Electron Transport Compound 3 was placed instill yet another molybdenum resistance heating boat. Subsequently, allboats were mounted onto the vacuum deposition apparatus.

Subsequently, after reducing the pressure of the vacuum tank to 4×10-4Pa, the aforesaid heating boat incorporating α-NPD was electricallyheated, and vacuum deposition was carried out onto the positive holetransport layer at a vacuum deposition rate of 0.1 nm/second, whereby apositive hole transport layer 2 was prepared. Further, the aforesaidboats, each incorporating H33 and Ir-26, were electrically heated, andco-vacuum deposition was carried at a vacuum deposition rate of 0.2nm/second and 0.012 nm/second, respectively, onto the aforesaid positivehole transport layer, whereby a light emitting layer was prepared.

Incidentally, during the aforesaid vacuum deposition, the substrate wasat room temperature. Further, the aforesaid boat incorporatingComparative Compound 5 was electrically heated, and vacuum depositionwas carried out onto the aforesaid light emitting layer at a vacuumdeposition rate of 0.1 nm/second, whereby an electron transport layerwas prepared. During the aforesaid vacuum deposition, the substrate wasat room temperature.

Subsequently, 0.5 nm lithium fluoride and 110 nm aluminum werevacuum-deposited to form a cathode, whereby Organic EL Element 6-1 wasprepared.

<<Preparation of Organic EL Elements 6-2-6-7>>

Organic EL Elements 6-2-6-7 were prepared in the same manner as OrganicEL Elements 6-1, except that Comparative Compound 5 was replaced witheach of the compounds described below in Table 4.

<<Evaluation of Organic EL Elements 6-1-6-7>>

Prepared Organic EL Elements 6-1-6-7 were evaluated as follows. Each ofthem was sealed in the same manner as Organic EL Element 1-1, andlighting devices shown in FIGS. 5 and 6 were formed and evaluated.

The prepared organic EL elements were evaluated as described below. Theresults are shown below.

(External Extraction Quantum Efficiency)

An organic EL element was allowed to emit light under conditions of roomtemperature (about 23-about 25° C.) and a constant electric current of2.5 mA/cm2. By determining emitted light luminance (L) (cd/m2), externalextraction efficiency (Ti) was calculated.

The above emitted light luminance was determined via CS-1000 (producedby Konica Minolta Sensing, Inc.). The external extraction quantumefficiency was represented by a relative value when Organic EL Element6-1 resulted in 100.

(Light Emission Lifetime)

An organic EL element was allowed to continuously emit light underconditions of room temperature and a constant electric current of 2.5mA/cm2, and the time (τ½), which was required to reach one half of theinitial luminance, was determined.

The light emission lifetime was represented by a relative value whenOrganic EL Element 6-1 resulted in 100.

The results are shown in the following table 4.

TABLE 4 External Extraction Electron Quantum Element TransportEfficiency Lifetime No. Compound (%) (%) Remarks 6-1 Comparative 100 100Comparative Compound 5 Example 6-2 16 132 640 Present Invention 6-3 26127 560 Present Invention 6-4 32 125 550 Present Invention 6-5 102 120490 Present Invention 6-6 103 116 420 Present Invention 6-7 104 110 350Present Invention

As can be seen from the above, the elements of the present inventionexhibited excellent external extraction quantum efficiency and lifetimecharacteristics, compared to Comparative Example.

Example 7 Preparation of Organic EL Element 7-1

Organic EL Element 7-1 was prepared in the same manner as Organic ELElement 4-1, except that instead of Positive Hole Transport Material 1,a solution which was prepared by dissolving 5 mg of Positive HoleTransport Material 3 and 45 mg of Positive Hole Transport Material 4 in10 ml of toluene was employed, H32 was employed instead of H31, Ir-30was employed instead of Ir-1, and BCP was employed instead ofComparative Compound 1.

<<Preparation of Organic EL Elements 7-2-7-6>>

Organic EL Elements 7-2-7-6 were prepared in the same manner as OrganicEL Element 7-1, except that BCP was replaced with each of the compoundsdescribed below in Table 5.

<<Evaluation of Organic EL Element 7-1-7-6>>

Prepared Organic EL Elements 7-1-7-6 were evaluated as follows. Each ofthem was sealed in the same manner as Organic EL Element 1-1, andlighting devices shown in FIGS. 5 and 6 were formed and evaluated.

Prepared organic EL elements were evaluated. Table 5 shows the results.

(Emitted Light Luminance)

Emitted light luminance (cd/m2) was determined, when 4 V direct currentvoltage was applied to an organic EL element at room temperature (about23-about 25° C.),

(External Extraction Quantum Efficiency)

Under the condition of a constant electric current of 5 mA/cm2, theexternal extraction efficiency was obtained in the same manner asOrganic EL Elements 6-1-.

The emitted light luminance and the external extraction quantumefficiency each was represented by a relative value when Organic ELElement 7-1 resulted in 100.

(Voltage Increase Ratio)

When driven at a constant electric current of 6 mA/cm2, initial voltageand that after 100 hours were determined. The relative value of theinitial voltage to that after 100 hours was designated as a voltageincrease ratio.

The emitted light luminance and the external extraction quantumefficiency each was represented by a relative value when the result ofOrganic EL Element 7-1 resulted in 100.

The evaluation results are shown in Table 5.

TABLE 5 External Extraction Voltage Electron Quantum Increase ElementTransport Efficiency Lifetime Ratio No. Compound (%) (%) (%) Remarks 7-1BCP 100 100 122 Comp. 7-2 Comparative 114 130 135 Comp. Compound 6 7-3105 136 760 104 Inv. 7-4 106 133 640 104 Inv. 7-5 107 131 570 105 Inv.7-6 108 124 400 108 Inv. Comp.: Comparative Example, Inv.: PresentInvention

Based on the above, it was noted that the voltage increase ratio of theelements of the present invention was reduced and the storage stabilitywas enhanced. Further, with regard to elements, which resulted in thesurface density and the band gap within the range of the presentinvention, it was noted that the aforesaid performance was furtherenhanced, and the emitted light luminance was also enhanced.

Example 8 Preparation of Organic EL Element 8-1

Organic EL Element 8-1 was prepared in the same manner as Organic ELElement 4-1, except that H31 was replaced with H35, and Ir-1 wasreplaced with Ir-12, while Comparative Compound 1 was replaced withComparative Compound 7.

<<Organic EL Elements 8-2-8-4>>

Organic EL Elements 8-2-8-4 were prepared in the same manner as OrganicElement 8-1, except that Ir-12 and Comparative Compound 7 were changedto the compounds described in the following Table 6.

<<Evaluation of Organic EL Elements 8-1-8-4>>

Prepared Organic EL Elements 8-1-8-4 were evaluated as follows. Each ofthem was sealed in the same manner as Organic EL Element 1-1, andlighting devices shown in FIGS. 5 and 6 were formed and evaluated.

With regard to the prepared elements, the external extraction quantumefficiency under the condition of a constant electric current of 2.5mA/cm2, and the light emission lifetime were determined in the samemanner as Organic EL Elements 6-1-6-7.

Further, during continuous light emission under the condition of aconstant electric current of 2.5 mA/cm2, the resulting emitted lightcolor was visually evaluated. The results of each were represented byrelative values when Organic EL Element 8-1 resulted in 100.

The evaluation results are shown in Table 56.

TABLE 6 External Phospho- Extraction Ele- rescence Electron QuantumLife- Emitted ment Emitting Transport Efficiency time Light Re- No.Compound Compound (%) (%) Color marks 8-1 Ir-12 Comparative 100 100 BlueComp. Compound 7 8-2 Ir-12 22 108 160 Blue Inv. 8-3 Ir-24 22 113 710Blue Inv. 8-4 Ir-26 22 120 5700 blue Inv. Comp.: Comparative Example,Inv.: Present Invention

As can be seen from the above, the elements of the present inventionexhibited higher external extraction quantum efficiency and longerlifetime, compared to Comparative Example.

Example 9 Preparation of Organic EL Element 9-1

Organic EL Element 9-1 was prepared in the same manner as Organic ELElement 6-1, except that Exemplified Compound 10 was employed instead ofH33, Ir-18 was employed instead of Ir-26, and Comparative Compound 7 wasemployed instead of Comparative Compound 5.

<<Preparation of Organic EL Elements 9-2 and 9-3>>

Organic EL Elements 9-2 and 9-3 were prepared in the same manner asOrganic EL Element 9-1, except that the host compound and the electrontransport compound were changed to the compounds described below.

<<Evaluation of Organic EL Elements 9-1-9-3>>

When prepared Organic EL elements 9-1-9-3 were evaluated, sealing wascarried out in the same manner as for Organic El Element 1-1, wherebythe lighting devices, shown in FIGS. 5 and 6, were formed and evaluated.

The external extraction quantum efficiency under the condition of aconstant electric current of 2.5 mA/cm2 and the light emission lifetimeof the prepared elements were determined in the same manner as forOrganic EL Elements 6-1-6-7. Each of the results was represented by arelative value when Organic EL element 9-1 resulted in 100.

The evaluation results are shown in Table 7.

TABLE 7 External Extraction Electron Quantum Element Host TransportEfficiency Lifetime No. Compound Compound (%) (%) Remarks 9-1 10Comparative 100 100 Comp. Compound 7 9-2 10 33 109 480 Inv. 9-3 H48 33128 640 Inv. Comp.: Comparative Example, Inv.: Present Invention

As can be seen from the above, the elements of the present inventionexcelled in external extraction quantum efficiency and lifetime,compared to Comparative Example.

Example 10 Preparation of Organic EL Full-Color Display Device

FIG. 7 is a schematic constitutional view of an organic EL full-colordisplay device. After carrying out patterning at a pitch of 100 μm ontoa substrate (NA45, produced by NH Techno Glass Corp.) on which a 100 nmfilm of ITO transparent electrode (102) was formed as an anode on glasssubstrate 101, a light-insensitive polyimide partition wall 103 (at awidth of 20 μm and a thickness of 2.0 μm) was formed viaphotolithography between the ITO transparent electrodes on the aforesaidglass substrate.

The positive hole injection layer composition composed, as describedbelow, was discharged and injected between the polyimide partition wallson the ITO electrode, employing an ink-jet head (MJ800C, produced byEPSON Co., exposed to ultraviolet radiation for 150 seconds, and driedat 60° C. for 10 minutes, whereby a 40 nm thick positive hole injectionlayer was prepared.

Each of the following blue light emitting layer composition, green lightemitting layer composition, and red light emitting layer composition wasdischarged and injected onto the aforesaid positive hole injectionlayer, employing an ink-jet head, and dried at 60° C. for 10 minutes,whereby each of the light emitting layers (105B, 105G, and 105R) wasformed. Subsequently, 20 nm 110 was vacuum-deposited to cover the lightemitting layer, and further, 0.6 nm lithium fluoride and 130 nm Al(106), as a cathode, were vacuum-deposited, whereby an organic ELelement was prepared.

By applying voltage to each electrode of the prepared organic ELelements, blue, green, and red lights were emitted, whereby availabilitywas noted as a full-color display device.

(Positive Hole Injection Layer Composition)

Positive Hole Transport Material 5 20 parts by weight Cyclohexylbenzene50 parts by weight Isopropylbiphenyl 50 parts by weight

(Blue Light Emitting Layer Composition)

H4 0.7 part by weight Ir-26 0.04 part by weight Cyclohexylbenzene 50parts by weight Isopropylbiphenyl 50 parts by weight

(Green Light Emitting Layer Composition)

H4 0.7 part by weight Ir-1 0.04 part by weight Cyclohexylbenzene 50parts by weight Isopropylbiphenyl 50 parts by weight

(Red Light Emitting Layer Composition)

H4 0.7 part by weight Ir-18 0.04 part by weight Cyclohexylbenzene 50parts by weight Isopropylbiphenyl 50 parts by weight

Example 11 Preparation of White Light Emitting Element 11-1

After carrying out patterning onto a substrate (NA-45, produced by NHTechno Glass Corp.) which was prepared by forming a 100 nm ITO (indiumtin oxide) film as an anode on the aforesaid 100 mm×100 mm×1.1 mm glass,the above transparent supporting substrate arranged with the ITOtransparent electrode was subjected to ultrasonic wave washing withisopropyl alcohol, was dried via desiccated nitrogen gas, and then wassubjected to UV ozone washing for 5 minutes.

A film was formed on the resulting transparent supporting substrate viaa spin coating method at 3,000 rpm and 30 seconds, employing a solutionprepared by diluting poly(3,4-ethylenedioxythiophen)-polystyrenesulfonate (PEDOT/PSS, BAYTRON P A1 4083, produced by Bayer Co.,) to 70%via pure water. Thereafter, drying was carried out at 200° C. for onehour, whereby a 30 nm thick first positive hole transport layer wasprepared.

The resulting substrate was transferred into a nitrogen atmosphere, anda film was formed on the first positive hole transport layer via thespin coating method, under conditions of 10,000 rpm and 30 seconds,applying a solution prepared by dissolving 50 mg of Positive HoleTransport Material 6 in 10 ml of toluene onto the above first positivehole transport layer. After carrying out photopolymerization andcross-linkage via exposure to ultraviolet radiation for 180 seconds,vacuum drying was carried out at 60° C. for one hour, a second positivehole transport layer was formed.

Subsequently, a film was formed via the spin coating method underconditions of 1,000 rpm and 30 seconds, employing a solution prepared bydissolving H32 (60 mg), Ir-9 (3.0 mg), and Ir-24 (3.0 mg) in 6 ml oftoluene. The resulting film was subjected to vacuum drying at 60° C. forone hour, whereby a light emitting layer was formed.

Furthermore, a film was formed via the spin coating method underconditions of 1,500 rpm and 30 seconds, employing a solution prepared bydissolving 111 (30 mg) in 5 ml of hexafluoroisopropanol (HFIP).Thereafter, the resulting film was subjected to vacuum drying at 60° C.for one hour, whereby a first electron transport layer was formed.

Subsequently, the aforesaid substrate was fixed onto the substrateholder of a vacuum deposition. In a molybdenum resistance heating boat,placed was 200 mg of Alq3 and the boat was mounted on the vacuumdeposition apparatus. After reducing the pressure of the vacuum tank to4×10-4 Pa, the boat incorporating Alq3 was electrically heated, andvacuum deposition was carried out onto the first electron transportlayer at a deposition rate of 0.1 nm/second, whereby a 40 nm thicksecond electron transport layer was further prepared.

Incidentally, during the deposition, the substrate was at roomtemperature.

Subsequently, 0.5 nm lithium fluoride and 110 nm aluminum weredeposited, whereby Organic EL Element 11-1 was prepared.

When the resulting element was electrically driven, almost pure whitelight was emitted and it was found to be employable as a lightingdevice. In addition, it was noticed that even though replaced with anyof the other exemplified compounds, similar white light was emitted.

1. An organic electroluminescent element comprising a substrate havingthereon an anode, a cathode, and a plurality of organic layerssandwiched between the anode and the cathode, wherein the plurality oforganic layers comprise: a light emitting layer containing aphosphorescence emitting compound; and an electron transport layercontaining a compound represented by Formula (1):(Ar1)n1−Y1  Formula (1) wherein n1 is an integer of 1 or more; Y1 is anaryl group or a heteroaryl group; Ar1 is a group represented by Formula(A), a plurality of Ar1 may be the same or different with each otherwhen n1 is two or more:

wherein X is —N(R)—, —O—, —S— or —Si(R)(R′)—; E1 to E8 each are —C(R1)═or —N═; R, R′ and R1 each are a hydrogen atom, a substituent or abonding site to Y1, (*) is a bonding site to Y1; Y2 is a single bond; Y3and Y4 each are a group derived from a 6 membered aromatic ring, atleast one of Y3 and Y4 is derived from an aromatic heterocyclic ringcontaining a nitrogen atom in the ring; and n2 is an integer of 1 to 4.2. The organic electroluminescent element of claim 1, wherein Y1 inFormula (1) is a heteroaryl group.
 3. The organic electroluminescentelement of claim 1, wherein the compound represented by Formula (1)contains at least two condensed aromatic heterocyclic rings eachcomprising 3 or more rings condensed with each other.
 4. The organicelectroluminescent element of claim 1, wherein Y1 of Formula (1) is agroup derive from a condensed aromatic heterocyclic ring comprising 3 ormore rings condensed with each other.
 5. The organic electroluminescentelement of claim 4, wherein Y1 of Formula (1) is a group derived from adibenzofuran ring or a dibenzothiophene ring.
 6. The organicelectroluminescent element of claim 1, wherein at least 6 of E1 to E8 ofFormula (A) are —C(R1)═.
 7. The organic electroluminescent element ofclaim 1, wherein Y4 of Formula (1) is a group derived from an aromaticheterocyclic ring containing a nitrogen atom in the ring.
 8. The organicelectroluminescent element of claim 6, wherein Y4 of Formula (1) is agroup derived from a pyridine ring.
 9. The organic electroluminescentelement of claim 1, wherein Y3 of Formula (1) is a group derived from abenzene ring.
 10. The organic electroluminescent element of claim 1,wherein n2 of Formula (A) is an integer of 1 to 2.